The Nordic medical birth registers--a potential goldmine for clinical research

Intrapartum fetal monitoring practices in Norway: A population-based study

OBJECTIVE

To describe intrapartum fetal monitoring methods used in all births in Norway in 2019-2020, assess adherence to national guidelines, investigate variation by women's risk status, and explore associations influencing monitoring practices.

METHODS

A nationwide population-based study. We collected data about all pregnancies with a gestational age ≥ 22 weeks during 2019-2020 from the Medical Birth Registry of Norway. We used descriptive analyses, stratified for risk status, to examine fetal monitoring methods used in all deliveries. Univariable and multivariable logistic regression models were used to determine factors associated with monitoring with cardiotocography (CTG) in low-risk, straightforward births.

RESULTS

In total, 14 285 (14%) deliveries were monitored with only intermittent auscultation (IA), 46214 (46%) with only CTG, and 33417 (34%) with IA and CTG combined. Four percent (2 067/50 533) of women with risk factors were monitored with IA only. Half (10589/21 282) of the low-risk women with straightforward births were monitored with CTG. Maternal and fetal characteristics, size of the birth unit and regional practices influenced use of CTG monitoring in this group.

CONCLUSIONS

Most births are monitored with CTG only, or combined with IA. Half the women with low-risk pregnancies and straightforward births were monitored with CTG although national guidelines recommending IA.

Obstetric anal sphincter injuries during instrumental vaginal delivery: An observational study based on 18-years of real-world data

OBJECTIVE

To determine the prevalence and secular trends of obstetric anal sphincter injuries (OASIS) in vacuum and forceps deliveries in Norway, both with and without episiotomy.

DESIGN

Population-based real-world data collected during 2001-2018.

SETTING

Medical Birth Registry Norway.

POPULATION OR SAMPLE

Nulliparous women with singleton foetuses in a cephalic presentation delivered by either vacuum or forceps (n = 70 783).

METHODS

Logistic regression analyses were applied to the OASIS prevalence in six 3-year time periods. Both crude odds ratios and adjusted odds ratios (aORs) with 95% confidence intervals (CIs) were determined.

MAIN OUTCOME MEASURES

OASIS prevalence.

RESULTS

The OASIS prevalence in vacuum and forceps deliveries decreased from 14.8% during 2001-2003 to 5.2% during 2016-2018. The overall reduction between the first and last 3-year time period was 61% (aOR = 0.39, 95% CIs = 0.35-0.43). The only exception to this decreasing trend in OASIS was found in forceps deliveries performed without an episiotomy. The OASIS prevalence was approximately twofold higher in forceps compared to vacuum deliveries (aOR = 1.92, 95% CIs = 1.79-2.05). Performing either a mediolateral or lateral episiotomy was associated with a 45% decrease in the prevalence of OASIS relative to no episiotomy (aOR = 0.55, 95% CIs = 0.52-0.58).

CONCLUSIONS

Opting for vacuum rather than forceps delivery in conjunction with a mediolateral or lateral episiotomy could significantly lower the OASIS prevalence in nulliparous women.

Gestational age at birth and type 1 diabetes in childhood and young adulthood: a nationwide register study in Finland, Norway and Sweden

AIMS/HYPOTHESIS

Children and adults born preterm have an increased risk of type 1 diabetes. However, there is limited information on risk patterns across the full range of gestational ages, especially after extremely preterm birth (23-27 weeks of gestation). We investigated the risk of type 1 diabetes in childhood and young adulthood across the full range of length of gestation at birth.

METHODS

Data were obtained from national registers in Finland, Norway and Sweden. In each country, information on study participants and gestational age was collected from the Medical Birth Registers, information on type 1 diabetes diagnoses was collected from the National Patient Registers, and information on education, emigration and death was collected from the respective national register sources. Individual-level data were linked using unique personal identity codes. The study population included all individuals born alive between 1987 and 2016 to mothers whose country of birth was the respective Nordic country. Individuals were followed until diagnosis of type 1 diabetes, death, emigration or end of follow-up (31 December 2016 in Finland, 31 December 2017 in Norway and Sweden). Gestational age was categorised as extremely preterm (23-27 completed weeks), very preterm (28-31 weeks), moderately preterm (32-33 weeks), late preterm (34-36 weeks), early term (37-38 weeks), full term (39-41 weeks; reference) and post term (42-45 weeks). HRs and 95% CIs from country-specific covariate-adjusted Cox regression models were combined in a meta-analysis using a common-effect inverse-variance model.

RESULTS

Among 5,501,276 individuals, 0.2% were born extremely preterm, 0.5% very preterm, 0.7% moderately preterm, 4.2% late preterm, 17.7% early term, 69.9% full term, and 6.7% post term. A type 1 diabetes diagnosis was recorded in 12,326 (0.8%), 6364 (0.5%) and 16,856 (0.7%) individuals at a median age of 8.2, 13.0 and 10.5 years in Finland, Norway and Sweden, respectively. Individuals born late preterm or early term had an increased risk of type 1 diabetes compared with their full-term-born peers (pooled, multiple confounder-adjusted HR 1.12, 95% CI 1.07, 1.18; and 1.15, 95% CI 1.11, 1.18, respectively). However, those born extremely preterm or very preterm had a decreased risk of type 1 diabetes (adjusted HR 0.63, 95% CI 0.45, 0.88; and 0.78, 95% CI 0.67, 0.92, respectively). These associations were similar across all three countries.

CONCLUSIONS/INTERPRETATION

Individuals born late preterm and early term have an increased risk of type 1 diabetes while individuals born extremely preterm or very preterm have a decreased risk of type 1 diabetes compared with those born full term.

A population-based cohort of drug exposures and adverse pregnancy outcomes in China (DEEP): rationale, design, and baseline characteristics

The DEEP cohort is the first population-based cohort of pregnant population in China that longitudinally documented drug uses throughout the pregnancy life course and adverse pregnancy outcomes. The main goal of the study aims to monitor and evaluate the safety of drug use through the pregnancy life course in the Chinese setting. The DEEP cohort is developed primarily based on the population-based data platforms in Xiamen, a municipal city of 5 million population in southeast China. Based on these data platforms, we developed a pregnancy database that documented health care services and outcomes in the maternal and other departments. For identifying drug uses, we developed a drug prescription database using electronic healthcare records documented in the platforms across the primary, secondary and tertiary hospitals. By linking these two databases, we developed the DEEP cohort. All the pregnant women and their offspring in Xiamen are provided with health care and followed up according to standard protocols, and the primary adverse outcomes - congenital malformations - are collected using a standardized Case Report Form. From January 2013 to December 2021, the DEEP cohort included 564,740 pregnancies among 470,137 mothers, and documented 526,276 live births, 14,090 miscarriages and 6,058 fetal deaths/stillbirths and 25,723 continuing pregnancies. In total, 13,284,982 prescriptions were documented, in which 2,096 chemicals drugs, 163 biological products, 847 Chinese patent medicines and 655 herbal medicines were prescribed. The overall incidence rate of congenital malformations was 2.0% (10,444/526,276), while there were 25,526 (4.9%) preterm births and 25,605 (4.9%) live births with low birth weight.

Placental weight percentile curves in a Danish population

INTRODUCTION

The role of the placenta is to transport oxygen and nutrients to the fetus, and a well-functioning placenta is vital to fetal health. Our aim was to develop placental weight percentile curves adjusted by gestational age, and stratified by major maternal comorbidities.

MATERIAL AND METHODS

The study was a population study in a Danish cohort. Data was drawn from The Medical Birth Register and the National Patient Register. We included singleton births with a gestational age of 22 + 0 to 42 + 6 weeks. We excluded multiple pregnancies, stillbirths and retained placentas. A total of 611 418 placentas were included. Percentile line graphs were created in groups of all placentas, hypertensive disorders and diabetic disorders.

RESULTS

Tables and figures are presented for placental weight percentile curves according to gestational age for all placentas, hypertensive disorders and diabetic disorders, respectively. Placental weight was generally higher in the diabetic placentas, and lower in the hypertensive placentas.

CONCLUSIONS

These percentile curves may serve as a reference for other populations, and may be useful for other studies investigating the role of the placenta in relation to pregnancy outcomes, and health in later life.

National routine data for low birthweight and preterm births: Systematic data quality assessment for United Nations member states (2000-2020)

OBJECTIVE

Low birthweight (<2500 g) and preterm birth (<37 weeks) are markers of newborn vulnerability. To facilitate informed decisions about investments in prevention and care, it is imperative to enhance data quality and use. Hence, the objective of this study is to systematically assess the quality of data concerning low birthweight and preterm births within routine administrative data sources.

DESIGN

Systematic data quality assessment by adopting the WHO Data Quality Framework.

SETTING

National routine data system from UN member states.

POPULATION

Livebirths.

METHODS

National routine administrative data on low birthweight and preterm births for 195 countries from 2000 to 2020 were systematically collated, totalling >700 million live births. The WHO data quality framework was adapted to undertake standardised data quality assessments.

MAIN OUTCOME MEASURES

Availability, reporting quality, internal and external consistency of low birthweight and preterm data.

RESULTS

Most United States Member States (64%: 124/195) had national data on low birthweight and (40%: 82/195) had data on preterm birth. Routine data system reporting was highest in North America, Australasia and Europe, where more than 95% live births had data on low birthweight and over 75% had data preterm births. In contrast, data reporting was lowest in sub-Saharan Africa (13% for low birthweight, 8% for preterm births) and Southern Asia (16% for low birthweight, 5% for preterm births). Most countries collect individual-level data; but, aggregate data reporting from hospital-based systems remain common in sub-Saharan Africa and Southern Asia. While data quality was generally high in North America, Australasia and Europe, gaps remain in the availability of gestational age metadata. Consistency between low birthweight and preterm rates were poor in Southern Asia and sub-Saharan Africa regions across time. There was high external consistency between low birthweight rates obtained from routine administrative data compared with low birthweight rates obtained from survey data for countries with high data quality.

CONCLUSIONS

Sub-Saharan Africa and South Asia countries have data gaps but also opportunities for rapid progress. Most births occure in facilities, electronic health information systems already include low birthweight, and adding accurate gestational age including with ultrasound assessment is becoming increasingly attainable. Moving toward the collection of individual level data would enable monitoring of quality of care and longer-term outcomes. This is crucial for every child and family and essential for measuring progress towards relevant sustainable development goals. The assessment will inform countries' actions for data quality improvement at national level and use of data for impact.

Very low birthweight infants receive less enteral feeding than what is prescribed

AIM

Feeding a very low birthweight (VLBW, <1500 g) infant is challenging. Our aims were to study how prescribed enteral feeding is implemented in VLBW infants and to identify factors associating with slow enteral feeding progression.

METHODS

Our retrospective cohort included 516 VLBW infants born before 32 weeks of gestation during 2005-2013 and admitted to Children's Hospital, Helsinki, Finland, for at least the two first weeks of life. Nutritional data were collected from birth until the age of 14-28 days, depending on the length of stay.

RESULTS

We found that enteral feeding progressed slower than recommended and implementation differed from the prescriptions, especially during the parenteral nutrition phase (milk intake 10-20 mL/kg/day): 71% [40-100], median [IQR], of the prescribed enteral milk was administered. The full prescribed amount was less likely administered if a higher volume of gastric residual was aspirated or if the infant did not pass stool during the same day. Longer opiate use, patent ductus arteriosus, respiratory distress syndrome and slower passage of the first meconium associated with slower enteral feeding progression.

CONCLUSION

Enteral feeding of a VLBW infant is often not administered as prescribed, which possibly plays a significant role in the slow progression of enteral feeding.

Mothers' Views on the Storage and Usage of Their Children's Biological Material Under the Danish Biobanking Model: A Narrative Approach Using Epistemic Injustice

OBJECTIVES

To investigate the knowledge and attitudes of mothers living in Denmark on the storage and usage of their children's biological material. The Danish Neonatal Screening Biobank contains blood from the Phenylketonuria-screening test. Legal, ethical, and moral concerns have been raised in several countries of how consent is obtained best in pediatric biobank governance. Research on knowledge and attitudes of Danish parents on the usage of their children's biological material is scarce.

METHODS

A coproduced study between a mother and 2 researchers. We analyzed 5 online focus group interviews using Ricoeur's hermeneutical narrative analysis.

RESULTS

Mothers have very little knowledge on the storage and usage of their children's biological material. They consider the Phenylketonuria-screening test to be part of a birth package, which leaves very little option of choice. They accept donating the material as a token of appreciation in an act of altruism toward the wider society but are only comfortable supporting Danish research.

CONCLUSIONS

An exploration of the communal narrative build in the interviews reveal an overall feeling of duty to help benefit society, an overwhelming trust toward the health system, and epistemic unjust storage information practices.

Reproduction patterns among non-Hodgkin lymphoma survivors by subtype in Sweden, Denmark and Norway: A population-based matched cohort study

Previous studies concerning reproductive patterns among non-Hodgkin lymphoma (NHL) survivors are scarce and those available have reported conflicting results. Treatment regimens vary considerably between aggressive and indolent NHL and studies of reproductive patterns by subtypes are warranted. In this matched cohort study, we identified all NHL patients aged 18-40 years and diagnosed between 2000 and 2018 from the Swedish and Danish lymphoma registers, and the clinical database at Oslo University Hospital (n = 2090). Population comparators were matched on sex, birth year and country (n = 19 427). Hazard ratios (HRs) were estimated using Cox regression. Males and females diagnosed with aggressive lymphoma subtypes had lower childbirth rates (HRfemale : 0.43, 95% CI: 0.31-0.59, HRmale : 0.61, 95% CI: 0.47-0.78) than comparators during the first 3 years after diagnosis. For indolent lymphomas, childbirth rates were not significantly different from comparators (HRfemale : 0.71, 95% CI: 0.48-1.04, HRmale : 0.94, 95% CI: 0.70-1.27) during the same period. Childbirth rates reached those of comparators for all subtypes after 3 years but the cumulative incidence of childbirths was decreased throughout the 10-year follow-up for aggressive NHL. Children of NHL patients were more likely to be born following assisted reproductive technology than those of comparators, except for male indolent lymphoma patients. In conclusion, fertility counselling is particularly important for patients with aggressive NHL.

Preterm birth and asthma and COPD in adulthood: a nationwide register study from two Nordic countries

BACKGROUND

Preterm birth affects lungs in several ways but few studies have follow-up until adulthood. We investigated the association of the entire spectrum of gestational ages with specialist care episodes for obstructive airway disease (asthma and chronic obstructive pulmonary disease (COPD)) at age 18-50 years.

METHODS

We used nationwide registry data on 706 717 people born 1987-1998 in Finland (4.8% preterm) and 1 669 528 born 1967-1999 in Norway (5.0% preterm). Care episodes of asthma and COPD were obtained from specialised healthcare registers, available in Finland for 2005-2016 and in Norway for 2008-2017. We used logistic regression to estimate odds ratios (ORs) for having a care episode with either disease outcome.

RESULTS

Odds of any obstructive airway disease in adulthood for those born at <28 or 28-31 completed weeks were 2-3-fold of those born full term (39-41 completed weeks), persisting after adjustments. For individuals born at 32-33, 34-36 or 37-38 weeks, the odds were 1.1- to 1.5-fold. Associations were similar in the Finnish and the Norwegian data and among people aged 18-29 and 30-50 years. For COPD at age 30-50 years, the OR was 7.44 (95% CI 3.49-15.85) for those born at <28 weeks, 3.18 (95% CI 2.23-4.54) for those born at 28-31 weeks and 2.32 (95% CI 1.72-3.12) for those born at 32-33 weeks. Bronchopulmonary dysplasia in infancy increased the odds further for those born at <28 and 28-31 weeks.

CONCLUSION

Preterm birth is a risk factor for asthma and COPD in adulthood. The high odds of COPD call for diagnostic vigilance when adults born very preterm present with respiratory symptoms.

Prenatal opioid exposure and risk of asthma in childhood: a population-based study from Denmark, Norway, and Sweden

Background: Opioids may modulate the immune function through opioid receptors on immune cells. Long-term consequences of prenatal opioid exposure on the immune system, such as childhood asthma, are unknown. Objectives: To investigate whether prenatal opioid exposure is associated with the risk of childhood asthma. Methods: Cohort study using linked nationwide registers in Denmark (1996-2015), Norway (2005-2015), and Sweden (2006-2013). Children born by mothers who were chronic opioid analgesics users before pregnancy (n = 14,764) or who were receiving opioid maintenance therapy (OMT) before or during pregnancy (n = 1,595) were identified based on information from each of the medical birth registers and prescription registers. Long-term opioid analgesics exposed children were compared to short-term exposed or unexposed, whereas OMT exposed children were compared to OMT unexposed. Asthma among children ≥1 years of age was defined as two or more filled prescriptions of antiasthmatic medication within 365 days, or a diagnosis of asthma. Hazard ratios (HRs) were calculated using Cox proportional hazards regression with attained age as the time scale. Inverse probability of treatment weights based on propensity scores were applied to adjust for measured confounders. Individual level data from Norway and Sweden were pooled, whereas individual level data from Denmark were analyzed separately. For the opioid analgesics comparisons, adjusted HRs (aHR) from the combined Norwegian/Swedish data and the Danish data were pooled in a fixed-effects meta-analysis. Results: For the opioid analgesics cohort, no increased risk of asthma was observed in long-term exposed children neither compared with unexposed [aHR = 0.99 (95% CI 0.87-1.12)], nor compared with short-term exposed [aHR = 0.97 (0.86-1.10)]. No increased risk of asthma was observed in OMT exposed compared with OMT unexposed children [Norway/Sweden: aHR = 1.07 (0.60-1.92), Denmark: aHR = 1.25 (0.87-1.81)]. Results from sensitivity analyses, where potential misclassification of the outcome and misclassification of OMT exposure were assessed, as well as starting follow-up at 6 years of age, showed that the estimates of association were generally robust. Conclusion: We found no association between prenatal exposure to opioids and risk of childhood asthma. Results were consistent across two different opioid exposure groups with different confounder distributions.

Effect of the maternal childbirth experience on a subsequent birth: a retrospective 7-year cohort study of primiparas in Finland

OBJECTIVE

To study the effect of the childbirth experience on the likelihood and interval to a subsequent live birth.

DESIGN

Retrospective analysis of a 7-year cohort.

SETTING

Childbirths in Helsinki University Hospital delivery units.

PARTICIPANTS

All parturients giving birth to a term and living baby from a single pregnancy in Helsinki University Hospital delivery units from January 2012 to December 2018 (n=120 437). Parturients delivering their first child (n=45 947) were followed until the birth of a subsequent child or the end of 2018.

MAIN OUTCOME MEASURE

The interval to a subsequent childbirth connected to the experience of the first childbirth was the primary outcome of the study.

RESULTS

A negative first childbirth experience decreases the likelihood of delivering a subsequent child during the follow-up (adjusted HR=0.81, 95% CI 0.76 to 0.86) compared with those experiencing the first childbirth as positive. For parturients with a positive childbirth experience, the median interval to a subsequent delivery was 3.90 years (3.84-3.97) compared with 5.29 years (4.86-5.97) after a negative childbirth experience.

CONCLUSION

The negative childbirth experience influences reproductive decisions. Consequently, more focus should be placed on understanding and managing the antecedents of positive/negative childbirth experiences.

Risk factors for and pregnancy outcomes after SARS-CoV-2 in pregnancy according to disease severity: A nationwide cohort study with validation of the SARS-CoV-2 diagnosis

INTRODUCTION

We identified risk factors and outcomes associated with SARS-CoV-2 infection in pregnancy in a universally tested population according to disease severity and validated information on SARS-CoV-2 during pregnancy in national health registers in Denmark.

MATERIAL AND METHODS

Cohort study using data from national registers and medical records including all pregnancies between March 1, 2020 and February 28, 2021. We compared women with a validated positive SARS-CoV-2 test during pregnancy with non-infected pregnant women. Risk factors and pregnancy outcomes were assessed by Poisson and Cox regression models and stratified according to disease severity defined by hospital admission status and admission reason (COVID-19 symptoms or other). Using medical record data on actual period of pregnancy, we calculated predictive values of the SARS-CoV-2 diagnosis in pregnancy in the registers.

RESULTS

SARS-CoV-2 infection was detected in 1819 (1.6%) of 111 185 pregnancies. Asthma was associated with infection (relative risk [RR] 1.63, 95% confidence interval [CI] 1.28-2.07). Risk factors for severe COVID-19 disease requiring hospital admission were high body mass index (median ratio 1.06, 95% CI 1.04-1.09), asthma (RR 7.47, 95% CI 3.51-15.90) and gestational age at the time of infection (gestational age 28-36 vs < 22: RR 3.53, 95% CI 1.75-7.10). SARS-CoV-2-infected women more frequently had hypertensive disorders in pregnancy (adjusted hazard ratio [aHR] 1.31, 95% CI 1.04-1.64), early pregnancy loss (aHR 1.37, 95% CI 1.00-1.88), preterm delivery before gestational age 28 (aHR 2.31, 95% CI 1.01-5.26), iatrogenically preterm delivery before gestational age 37 (aHR 1.49, 95% CI 1.01-2.19) and small-for-gestational age children (aHR 1.28, 95% CI 1.05-1.54). The associations were stronger among women admitted to hospital for any reason. The validity of the SARS-CoV-2 diagnosis in relation to pregnancy in the registers compared with medical records showed a negative predictive value of 99.9 (95% CI 99.9-100.0) and a positive predictive value of 82.1 (95% CI 80.4-83.7).

CONCLUSIONS

Women infected with SARS-CoV-2 during pregnancy were at increased risk of hypertensive disorders in pregnancy, early pregnancy loss, preterm delivery and having children small for gestational age. The validity of Danish national registers was acceptable for identification of SARS-CoV-2 infection during pregnancy.

Different pathways for preterm birth between singleton and twin pregnancies: a population-based registry study of 481 176 nulliparous women

OBJECTIVE

To explore the contribution of pregnancy-related complications on the prevalence of extremely, very and late preterm births in singleton and twin pregnancies. To study the risk of spontaneous preterm birth in twin pregnancies compared with singleton pregnancies.

DESIGN

Population-based registry study.

SETTING

Medical birth registry of Norway and Statistics Norway.

POPULATION

Nulliparous women with singleton (n = 472 449) or twin (n = 8727) births during 1999-2018.

METHODS

Prevalence rates of pregnancy-related complications for extremely, very and late preterm birth in twin and singleton pregnancies were calculated with 95% confidence intervals. Multivariable logistic regression was applied to assess odds ratios for preterm birth, adjusted for obstetric and socio-economic factors.

MAIN OUTCOME MEASURES

Extremely preterm (<28⁺⁰  weeks of gestation), very preterm (28⁺⁰ -33⁺⁶  weeks of gestation) and late preterm (34⁺⁰ -36⁺⁶  weeks of geatation) birth.

RESULTS

Preterm birth was significantly more prevalent in twin pregnancies than in singleton pregnancies in all categories: all preterm (54.7% vs 6.1%), extremely preterm (3.6% vs 0.4%), very preterm (18.2% vs 1.4%) and late preterm (33.0% vs 4.3%) births. Stillbirth, congenital malformation and pre-eclampsia were more prevalent in twin pregnancies than in singleton pregnancies, but the prevalence of complications differed in the three categories of preterm birth. Pre-eclampsia was more prevalent in singleton than in twin pregnancies ending in extremely and very preterm birth. The adjusted odds of spontaneous preterm live birth were between 19- and 54-fold greater in twin pregnancies than in singleton pregnancies.

CONCLUSIONS

Singleton and twin pregnancies seem to have different pathways leading to extremely, very and late preterm birth.

Maternal age and the risk of low birthweight and pre-term delivery: a pan-Nordic comparison

BACKGROUND

Advanced maternal age at birth is considered a risk factor for adverse birth outcomes. A recent study applying a sibling design has shown, however, that the association might be confounded by unobserved maternal characteristics.

METHODS

Using total population register data on all live singleton births during the period 1999-2012 in Denmark (N = 580 133; 90% population coverage), Norway (N = 540 890) and Sweden (N = 941 403) and from 2001-2014 in Finland (N = 568 026), we test whether advanced maternal age at birth independently increases the risk of low birthweight (LBW) (<2500 g) and pre-term birth (<37 weeks gestation). We estimated within-family models to reduce confounding by unobserved maternal characteristics shared by siblings using three model specifications: Model 0 examines the bivariate association; Model 1 adjusts for parity and sex; Model 2 for parity, sex and birth year.

RESULTS

The main results (Model 1) show an increased risk in LBW and pre-term delivery with increasing maternal ages. For example, compared with maternal ages of 26-27 years, maternal ages of 38-39 years display a 2.2, 0.9, 2.1 and 2.4 percentage point increase in the risk of LBW in Denmark, Finland, Norway and Sweden, respectively. The same patterns hold for pre-term delivery.

CONCLUSIONS

Advanced maternal age is independently associated with higher risk of poor perinatal health outcomes even after adjusting for all observed and unobserved factors shared between siblings.

Time trends in caesarean section rates and associations with perinatal and neonatal health: a population-based cohort study of 1 153 789 births in Norway

OBJECTIVES

To study caesarean section (CS) rates and associations with perinatal and neonatal health in Norway during 1999-2018.

DESIGN

Population-based cohort study.

SETTING

Medical Birth Registry of Norway.

PARTICIPANTS

1 153 789 births and 1 174 066 newborns.

METHODS

CS, intrapartum, perinatal and neonatal mortality rates expressed as percentages (%) or per mille (‰) with 95% CIs.

PRIMARY AND SECONDARY OUTCOME MEASURES

CS rates in the Robson Ten-Group Classification System; intrapartum, perinatal and neonatal mortality rates.

RESULTS

The overall CS rate increased from 12.9% in 1999 to 16.7% in 2008 (p<0.001), and then reduced to 15.8% in 2018 (p<0.001). The largest reductions were observed in Robson groups 2 and 4. In Robson group 2, the planned CS rate decreased from 9.6% in 2007-2008 to 4.6% in 2017-2018, the intrapartum CS rate decreased from 26.6% in 2007-2008 to 22.3% in 2017-2018. In Robson group 4, the planned CS rate decreased from 16.1% in 2007-2008 to 7.6% in 2017-2018, and the intrapartum CS rate decreased from 7.8% in 2007-2008 to 5.2% in 2017-2018.The intrapartum fetal mortality rate decreased from 0.51 per 1000 (‰) in 1999-2000 to 0.14‰ in 2017-2018. Neonatal mortality decreased from 2.52‰ to 1.58‰.

CONCLUSIONS

CS rates in Norway increased between 1999 and 2008, followed by a significant reduction between 2008 and 2018. At the same time, fetal and neonatal mortality rates decreased. Norwegian obstetricians and midwives have contributed to maintaining a low CS rate under 17%. These findings indicate that restricting the use of CS is a safe option for perinatal health.

Labor epidural analgesia and subsequent risk of offspring autism spectrum disorder and attention-deficit/hyperactivity disorder: a cross-national cohort study of 4.5 million individuals and their siblings

BACKGROUND

A recent study has suggested that labor epidural analgesia may be associated with increased rates of offspring autism spectrum disorder. Subsequent replication attempts have lacked sufficient power to confidently exclude the possibility of a small effect, and the causal nature of this association remains unknown.

OBJECTIVE

This study aimed to investigate the extent to which exposure to labor epidural analgesia is associated with offspring autism spectrum disorder and attention-deficit/hyperactivity disorder following adjustments for unmeasured familial confounding.

STUDY DESIGN

We identified 4,498,462 singletons and their parents using the Medical Birth Registers in Finland (cohorts born from 1987-2005), Norway (1999-2015), and Sweden (1987-2011) linked with population and patient registries. These cohorts were followed from birth until they either had the outcomes of interest, emigrated, died, or reached the end of the follow-up (at mean ages 13.6-16.8 years), whichever occurred first. Cox regression models were used to estimate country-specific associations between labor epidural analgesia recorded at birth and outcomes (eg, at least 1 secondary care diagnosis of autism spectrum disorder and attention-deficit/hyperactivity disorder or at least 1 dispensed prescription of medication used for the treatment of attention-deficit/hyperactivity disorder). The models were adjusted for sex, birth year, birth order, and unmeasured familial confounders via sibling comparisons. Pooled estimates across all the 3 countries were estimated using inverse variance weighted fixed-effects meta-analysis models.

RESULTS

A total of 4,498,462 individuals (48.7% female) were included, 1,091,846 (24.3%) of which were exposed to labor epidural analgesia. Of these, 1.2% were diagnosed with autism spectrum disorder and 4.0% with attention-deficit/hyperactivity disorder. On the population level, pooled estimates showed that labor epidural analgesia was associated with increased risk of offspring autism spectrum disorder (adjusted hazard ratio, 1.12; 95% confidence interval, 1.10-1.14, absolute risks, 1.20% vs 1.07%) and attention-deficit/hyperactivity disorder (adjusted hazard ratio, 1.20; 95% confidence interval, 1.19-1.21; absolute risks, 3.95% vs 3.32%). However, when comparing full siblings who were differentially exposed to labor epidural analgesia, the associations were fully attenuated for both conditions with narrow confidence intervals (adjusted hazard ratio [autism spectrum disorder], 0.98; 95% confidence interval, 0.93-1.03; adjusted hazard ratio attention-deficit/hyperactivity disorder, 0.99; 95% confidence interval, 0.96-1.02).

CONCLUSION

In this large cross-national study, we found no support for the hypothesis that exposure to labor epidural analgesia causes either offspring autism spectrum disorder or attention-deficit/hyperactivity disorder.

Maternal Health, Pregnancy and Offspring Factors, and Maternal Thyroid Cancer Risk: A Nordic Population-Based Registry Study

Thyroid cancer incidence is higher in women than men, especially during the reproductive years, for reasons that remain poorly understood. Using population-based registry data from 4 Nordic countries through 2015, we examined associations of perinatal characteristics with risk of maternal thyroid cancer. Cases were women diagnosed with thyroid cancer ≥2 years after last birth (n = 7,425, 83% papillary). Cases were matched to controls (n = 67,903) by mother's birth year, country, and county of residence. Odds ratios (ORs) were estimated using conditional logistic regression models adjusting for parity. Older age at first pregnancy, postpartum hemorrhage (OR = 1.18, 95% (confidence interval) CI: 1.08, 1.29), and benign thyroid conditions (ORs ranging from 1.64 for hypothyroidism to 10.35 for thyroid neoplasms) were associated with increased thyroid cancer risk, as were higher offspring birth weight (per 1-kg increase, OR = 1.17, 95% CI: 1.12, 1.22) and higher likelihood of offspring being large for gestational age (OR = 1.26, 95% CI: 1.11, 1.43). Unmarried/noncohabiting status (OR = 0.91, 95% CI: 0.84, 0.98), maternal smoking (OR = 0.75, 95% CI: 0.67, 0.84), and preterm birth (OR = 0.90, 95% CI: 0.83, 0.98) were associated with reduced risk. Several factors (e.g., older age at first pregnancy, maternal smoking, goiter, benign neoplasms, postpartum hemorrhage, hyperemesis gravidarum, and neonatal jaundice) were associated with advanced thyroid cancer. These findings suggest that some perinatal exposures may influence maternal thyroid cancer risk.

Consortium for the Study of Pregnancy Treatments (Co-OPT): An international birth cohort to study the effects of antenatal corticosteroids

BACKGROUND

Antenatal corticosteroids (ACS) are widely prescribed to improve outcomes following preterm birth. Significant knowledge gaps surround their safety, long-term effects, optimal timing and dosage. Almost half of women given ACS give birth outside the "therapeutic window" and have not delivered over 7 days later. Overtreatment with ACS is a concern, as evidence accumulates of risks of unnecessary ACS exposure.

METHODS

The Consortium for the Study of Pregnancy Treatments (Co-OPT) was established to address research questions surrounding safety of medications in pregnancy. We created an international birth cohort containing information on ACS exposure and pregnancy and neonatal outcomes by combining data from four national/provincial birth registers and one hospital database, and follow-up through linked population-level data from death registers and electronic health records.

RESULTS AND DISCUSSION

The Co-OPT ACS cohort contains 2.28 million pregnancies and babies, born in Finland, Iceland, Israel, Canada and Scotland, between 1990 and 2019. Births from 22 to 45 weeks' gestation were included; 92.9% were at term (≥ 37 completed weeks). 3.6% of babies were exposed to ACS (67.0% and 77.9% of singleton and multiple births before 34 weeks, respectively). Rates of ACS exposure increased across the study period. Of all ACS-exposed babies, 26.8% were born at term. Longitudinal childhood data were available for 1.64 million live births. Follow-up includes diagnoses of a range of physical and mental disorders from the Finnish Hospital Register, diagnoses of mental, behavioural, and neurodevelopmental disorders from the Icelandic Patient Registers, and preschool reviews from the Scottish Child Health Surveillance Programme. The Co-OPT ACS cohort is the largest international birth cohort to date with data on ACS exposure and maternal, perinatal and childhood outcomes. Its large scale will enable assessment of important rare outcomes such as perinatal mortality, and comprehensive evaluation of the short- and long-term safety and efficacy of ACS.

Antidepressant Fill and Dose Trajectories in Pregnant Women with Depression and/or Anxiety: A Norwegian Registry Linkage Study

Background

Few studies investigated longitudinal antidepressant exposure during pregnancy and included dosage in the assessment.

Methods

We conducted a nationwide, registry-linkage study in Norway using data on antidepressant prescription fills in pregnancies lasting ≥32 weeks in women with a delivery between 2009 and 2018 who had a depression/anxiety diagnosis and antidepressant fills prior to pregnancy. Information on antidepressant exposure by week (measured by filled prescriptions) and prescribed average daily dose was used in longitudinal k-means trajectory modelling for a 108-week time window from six months prior to pregnancy to one year after delivery. Factors associated with trajectory group membership were examined using multinomial logistic regression models.

Results

We included 8,460 pregnancies in 8,092 women. Four antidepressant fill trajectories were identified based on filled antidepressant prescriptions: two distinct discontinuing patterns, one at around the start of pregnancy (30.4%) and one around the end of pregnancy (33.8%); one continuing pattern (20.6%); and one interrupting pattern (15.2%). Using average usual daily dose, we identified low dose discontinuing (60.3%), medium dose reducing (20.6%) and high dose continuing (15.2%) patterns. The multinomial logistic regressions showed that the fill trajectory group membership was strongly associated with: antidepressant type and dose prior to pregnancy and co-medication prior to pregnancy, maternal age, marital status, parity, previous pregnancy loss, and pregnancy planning.

Conclusion

Longitudinal trajectory modelling revealed distinct antidepressant fill and dosage patterns in the period around pregnancy. Knowledge about factors associated with utilization trajectories might be useful for health-care personnel counselling women about antidepressant use in pregnancy.

Duloxetine Exposure During Pregnancy and the Risk of Offspring Being Born Small for Gestational Age or Prematurely: A Nationwide Danish and Swedish Safety Study

BACKGROUND

Depression or depressive symptoms are common among pregnant women. The use of antidepressants during pregnancy has grown steadily. The risk of offspring being born small for gestational age or prematurely when exposed to duloxetine during pregnancy is not established.

OBJECTIVE

We aimed to investigate the association between duloxetine exposure during pregnancy and offspring being born small for gestational age or prematurely.

METHODS

We conducted an observational study including live births in Sweden and Denmark (2004-2016). Duloxetine exposure during early (0-140 days) or late (141 to delivery) pregnancy compared with duloxetine-non-exposed, selective serotonin reuptake inhibitor-exposed, venlafaxine-exposed, and duloxetine discontinuers.

RESULTS

In total, 2,083,467 pregnancies were identified, where 1589 and 450 were duloxetine exposed in early and late pregnancy, respectively. For small for gestational age, no increased risk was seen for duloxetine across comparators. In the early and late exposure windows, propensity score-matched odds ratios for small for gestational age ranged between 0.64 (95% confidence interval 0.44-0.95) and 1.48 (95% confidence interval 0.85-2.57). For preterm birth, the findings differed across comparators and exposure-time windows, but trended towards an increased risk for duloxetine-exposed when compared with duloxetine-non-exposed, selective serotonin reuptake inhibitor-exposed, and duloxetine discontinuers in both early exposure and late exposure. The odds ratios ranged between 1.17 and 2.04, of which some did not reach statistical significance. No clear association was observed when compared with venlafaxine exposed, 0.91 (95% confidence interval 0.73-1.14) for early exposure and 1.26 (95% confidence interval 0.86-1.86) for late exposure. Most preterm births (79.2%) occurred in weeks 33-36 of gestation.

CONCLUSIONS

Duloxetine exposure during pregnancy is unlikely to increase the risk of small for gestational age. Although not consequently statistically significant across comparisons, a trend towards an increased risk of preterm birth was observed for duloxetine exposed. Therefore, an increased risk of preterm birth cannot be excluded, especially for women exposed to duloxetine throughout pregnancy.

Sex differences in childhood cancer risk among children with major birth defects: a Nordic population-based nested case-control study

BACKGROUND

Childhood cancer is more common among children with birth defects, suggesting a common aetiology. Whether this association differs by sex is unclear.

METHODS

We performed a population-based nested case-control study using nationwide health registries in four Nordic countries. We included 21 898 cancer cases (0-19 years) and 218 980 matched population controls, born 1967-2014. Associations between childhood cancer and major birth defects were calculated as odds ratios (ORs) with 95% confidence intervals (CIs) using logistic regression models. Effect modification was evaluated using a counterfactual framework to estimate confidence intervals and P-values for the natural indirect effects.

RESULTS

Birth defects were present for 5.1% (1117/21 898) of childhood cancer cases and 2.2% (4873/218 980) of controls; OR of cancer was higher for chromosomal (OR = 10, 95% CI = 8.6-12) than for non-chromosomal defects (OR = 1.9, 95% CI = 1.8-2.1), strongest between genetic syndromes/microdeletion and renal tumours, Down syndrome and leukaemia, and nervous system defects and central nervous system tumours. The association between birth defects and cancer was stronger among females (OR = 2.8, 95% CI = 2.6-3.1) than males (OR = 2.1, 95% CI = 1.9-2.2, Pinteraction <0.001). Male sex was an independent risk factor for childhood cancer, but very little of the overall association between sex and childhood cancer was mediated through birth defects (4.8%, PNIE <0.001), although more at younger ages (10% below years and 28% below 1 year).

CONCLUSIONS

The birth defect-cancer associations were generally stronger among females than males. Birth defects did not act as a strong mediator for the modest differences in childhood cancer risk by sex, suggesting that other biological pathways are involved.

Trends in labor induction indications: A 20-year population-based study

INTRODUCTION

Use of labor induction has increased rapidly in most middle- and high-income countries over the past decade. The reasons for the stark rise in labor induction are largely unknown. We aimed to assess the extent to which the rising rate of labor induction is explained by changes in rates of underlying indications over time.

MATERIAL AND METHODS

The study was based on nationwide data from the Icelandic Medical Birth Register on 85 620 singleton births from 1997 to 2018. The rate of labor induction and indications for induction was calculated for all singleton births in 1997-2018. Change over time was expressed as relative risk (RR), using Poisson regression with 95% confidence intervals (CI) adjusted for maternal characteristics and indications for labor induction.

RESULTS

The crude rate of labor induction rose from 12.5% in 1997-2001 to 23.9% in 2014-2018 (crude RR = 1.91, 95% CI 1.81-2.01). While adjusting for maternal characteristics had little impact, adjusting additionally for labor induction indications lowered the RR to 1.43 (95% CI 1.35-1.51). Induction was increasingly indicated from 1997-2001 to 2014-2018 by gestational diabetes (2.4%-16.5%), hypertensive disorders (7.0%-11.1%), prolonged pregnancy (16.2%-23.7%), concerns for maternal wellbeing (3.2%-6.9%) and maternal age (0.5%-1.2%). No indication was registered for 9.2% of inductions in 2014-2018 compared with 16.3% in 1997-2001.

CONCLUSIONS

Our results show that the increase in labor induction over the study period is largely explained by an increase in various underlying conditions indicating labor induction. However, indications for 9.2% of labor inductions remain unexplained and warrant further investigation.

Cancer in children born after frozen-thawed embryo transfer: A cohort study

BACKGROUND

The aim was to investigate whether children born after assisted reproduction technology (ART), particularly after frozen-thawed embryo transfer (FET), are at higher risk of childhood cancer than children born after fresh embryo transfer and spontaneous conception.

METHODS AND FINDINGS

We performed a registry-based cohort study using data from the 4 Nordic countries: Denmark, Finland, Norway, and Sweden. The study included 7,944,248 children, out of whom 171,774 children were born after use of ART (2.2%) and 7,772,474 children were born after spontaneous conception, representing all children born between the years 1994 to 2014 in Denmark, 1990 to 2014 in Finland, 1984 to 2015 in Norway, and 1985 to 2015 in Sweden. Rates for any cancer and specific cancer groups in children born after each conception method were determined by cross-linking national ART registry data with national cancer and health data registries and population registries. We used Cox proportional hazards models to estimate the risk of any cancer, with age as the time scale. After a mean follow-up of 9.9 and 12.5 years, the incidence rate (IR) of cancer before age 18 years was 19.3/100,000 person-years for children born after ART (329 cases) and 16.7/100,000 person-years for children born after spontaneous conception (16,184 cases). Adjusted hazard ratio (aHR) was 1.08, 95% confidence interval (CI) 0.96 to 1.21, p = 0.18. Adjustment was performed for sex, plurality, year of birth, country of birth, maternal age at birth, and parity. Children born after FET had a higher risk of cancer (48 cases; IR 30.1/100,000 person-years) compared to both fresh embryo transfer (IR 18.8/100,000 person-years), aHR 1.59, 95% CI 1.15 to 2.20, p = 0.005, and spontaneous conception, aHR 1.65, 95% CI 1.24 to 2.19, p = 0.001. Adjustment either for macrosomia, birth weight, or major birth defects attenuated the association marginally. Higher risks of epithelial tumors and melanoma after any assisted reproductive method and of leukemia after FET were observed. The main limitation of this study is the small number of children with cancer in the FET group.

CONCLUSIONS

Children born after FET had a higher risk of childhood cancer than children born after fresh embryo transfer and spontaneous conception. The results should be interpreted cautiously based on the small number of children with cancer, but the findings raise concerns considering the increasing use of FET, in particular freeze-all strategies without clear medical indications.

TRIAL REGISTRATION

Trial registration number: ISRCTN 11780826.

Antidepressant and mental health care utilization in pregnant women with depression and/or anxiety: An interrupted time-series analysis

BACKGROUND

Little is known about mental health care utilization patterns in pregnant women with depression/anxiety in Norway according to antidepressant fill trajectories in pregnancy.

METHOD

We conducted a registry-linkage cohort study of pregnancies within women having outpatient visit for depression/anxiety and antidepressant fills prior to pregnancy identified from four national registries of Norway (2009-2018). Number of consultations for depression/anxiety per 100 pregnancies as proxy of mental health care utilization was modelled using interrupted time-series analysis with first month into pregnancy and first month after delivery as interruption points. We investigated the time window spanning from six months prior to one year postpartum. Antidepressant fill trajectories in the corresponding time window were identified using longitudinal k-means trajectory modelling.

RESULTS

The cohort included 8460 pregnancies within 8062 women with depression/anxiety. We observed reduced mental health care utilization when pregnant women entered the course of pregnancy (negative slopes during pregnancy for psychiatric specialists and psychologists). The declines were observed for all antidepressant fill trajectories (i.e., discontinuers and continuers) except interrupters (i.e., discontinued then resumed treatment). We found increased mental health care utilization in the postpartum year, notably in interrupters (positive slopes in consultation rates with specialists of outpatient clinics and public-contracted psychiatrists).

LIMITATIONS

It was not possible to measure directly the use of psychosocial interventions and psychotherapy.

CONCLUSIONS

Pregnancy was associated with reduced mental health care utilization regardless of whether antidepressant treatment was maintained during pregnancy or not. Increases in mental health care utilization were observed in the postpartum year, especially in interrupters.

Maternal childbirth experience and induction of labour in each mode of delivery: a retrospective seven-year cohort study of 95,051 parturients in Finland

Background

Childbirth experience has been shown to depend on the mode of delivery. However, it is unclear how labour induction influences the childbirth experience in different modes of delivery. Thus, we assessed the childbirth experience among mothers with spontaneous and induced labours.

Design

A retrospective cohort study.

Setting

Childbirths in four delivery hospitals in Helsinki and Uusimaa District, Finland, in 2012-2018.

Sample

95051 childbirths excluding elective caesarean sections.

Methods

Obstetric data combined to maternal childbirth experience measured by Visual Analogue Scale (VAS) was analysed with univariate linear modelling and group comparisons. The primiparas and multiparas were analysed separately throughout the study due to the different levels of VAS.

Main outcome measures

Maternal childbirth experience measured by VAS.

Results

The negative effect of labour induction on the childbirth experience was discovered in each mode of delivery. Operative deliveries were perceived more negatively when they were preceded by labour induction. The rate of poor childbirth experience (VAS≤5) was higher for mothers with labour induction (ORs varying from 1.43 to 1.77) except in emergency caesarean sections. The negative effect of labour induction was smaller than the effect of mode of delivery, while successful vaginal delivery with induction (mean_PRIMI=8.00 [95% CI 7.96–8.04], mean_MULTI=8.50 [8.47–8.53]) was perceived more positive than operational deliveries with spontaneous labour (means_PRIMI≤7.66 [7.61–7.70], means_MULTI≤7.96 [7.89–8.03]). However, labour induction more than doubled the risk of caesarean section for both primiparas and multiparas.

Conclusions

Labour induction generates more negative experiences for both primiparas and multiparas. The negative effect of labour induction is detected for all modes of delivery, being worst among labour induction resulting in operative delivery. The parturients facing cumulative obstetric interventions require special support and counselling during and after delivery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04830-9.

Risk of preterm birth in relation to history of preterm birth: a population-based registry study of 213 335 women in Norway

OBJECTIVE

To assess the association between preterm first birth and preterm second birth according to gestational age and to determine the role of placental disorder in recurrent preterm birth.

DESIGN

Population-based registry study.

SETTING

Medical Birth Registry of Norway and Statistics Norway.

POPULATION

Women (n = 213 335) who gave birth to their first and second singleton child during 1999-2014 (total n = 426 670 births).

METHODS

Multivariate logistic regression analyses, adjusted for placental disorders, maternal, obstetric and socio-economic factors.

MAIN OUTCOME MEASURES

Extremely preterm (<28+0  weeks), very preterm (28+0 -33+6  weeks) and late preterm (34+0 -36+6  weeks) second birth.

RESULTS

Preterm birth (<37 weeks) rates were 5.6% for first births and 3.7% for second births. Extremely preterm second births (0.2%) occurred most frequently among women with an extremely preterm first birth (aOR 12.90, 95% CI 7.47-22.29). Very preterm second births (0.7%) occurred most frequently after an extremely preterm birth (aOR 12.98, 95% CI 9.59-17.58). Late preterm second births (2.8%) occurred most frequently after a previous very preterm birth (aOR 6.86, 95% CI 6.11-7.70). Placental disorders contributed 30-40% of recurrent extremely and very preterm births and 10-20% of recurrent late preterm birth.

CONCLUSION

A previous preterm first birth was a major risk factor for a preterm second birth. The contribution of placental disorders was more pronounced for recurrent extremely and very preterm birth than for recurrent late preterm birth. Among women with any category of preterm first birth, more than one in six also had a preterm second birth (17.4%).

TWEETABLE ABSTRACT

Preterm first birth is a major risk factor for subsequent preterm birth, regardless of maternal, obstetric or fetal risk factors.

Substantial decrease in preeclampsia prevalence and risk over two decades: A population-based study of 1,153,227 deliveries in Norway

OBJECTIVES

Analyze secular trends of preeclampsia in Norway based on risk factors.

STUDY DESIGN

Population-based cohort study of 1,153,227 women using data from Medical Birth Registry of Norway from 1999 to 2018. Aggregated data from Norwegian Prescription Database from 2004 to 2018 were used. Main exposure variable was time period. Descriptive statistics identified the prevalence of preeclampsia, labor induction and aspirin use. Multiple logistic regression analysis was performed to estimate the risk of preeclampsia during the time periods.

MAIN OUTCOME MEASURES

Preeclampsia.

RESULTS

Overall preeclampsia prevalence decreased from 4.3% in 1999-2002 to 2.7% in 2015-2018. A reduction was observed in all subgroups of women with known risk factors (age, nulliparity, diabetes, chronic hypertension, assisted reproduction, twin pregnancy). Adjusted risk of preeclampsia was reduced by 44% from 1999-2002 to 2015-2018 (aOR = 0.56, 95%CI 0.54, 0.58), while the net prevalence of gestational hypertension remained stable over the study period. Labor induction increased 104%. Aspirin prescriptions increased among fertile women in the general Norwegian population.

CONCLUSIONS

Preeclampsia prevalence and risk were reduced regardless of risk factors and despite an increased proportion of high-risk parturients (advanced age, lower parity, use of assisted reproduction). A corresponding increase in aspirin prescriptions among fertile women and an overall increase in labor inductions were also observed, suggesting that clinical interventions may partly explain the observed reduction in preeclampsia prevalence. Lower average blood pressure and improved health in the population may also explain some of the reduction.

Gestational Age, Parent Education, and Education in Adulthood

BACKGROUND

Adults born preterm (<37 weeks) have lower educational attainment than those born term. Whether this relationship is modified by family factors such as socioeconomic background is, however, less well known. We investigated whether the relationship between gestational age and educational attainment in adulthood differed according to parents' educational level in 4 Nordic countries.

METHODS

This register-based cohort study included singletons born alive from 1987 up to 1992 in Denmark, Finland, Norway, and Sweden. In each study population, we investigated effect modification by parents' educational level (low, intermediate, high) on the association between gestational age at birth (25-44 completed weeks) and low educational attainment at 25 years (not having completed upper secondary education) using general estimation equations logistic regressions.

RESULTS

A total of 4.3%, 4.0%, 4.8%, and 5.0% singletons were born preterm in the Danish (n = 331 448), Finnish (n = 220 095), Norwegian (n = 292 840), and Swedish (n = 513 975) populations, respectively. In all countries, both lower gestational age and lower parental educational level contributed additively to low educational attainment. For example, in Denmark, the relative risk of low educational attainment was 1.84 (95% confidence interval 1.44 to 2.26) in adults born at 28 to 31 weeks whose parents had high educational level and 5.25 (95% confidence interval 4.53 to 6.02) in adults born at 28 to 31 weeks whose parents had low educational level, compared with a reference group born at 39 to 41 weeks with high parental educational level.

CONCLUSIONS

Although higher parental education level was associated with higher educational attainment for all gestational ages, parental education did not mitigate the educational disadvantages of shorter gestational age.

Use of interrupted time-series analysis to characterise antibiotic prescription fills across pregnancy: a Norwegian nationwide cohort study

OBJECTIVES

Antibiotics are the most frequently prescribed medications for pregnant and breastfeeding women. We applied interrupted time-series analysis (ITSA) to describe antibiotic prescription fills patterns in pregnant women and examined recurrent antibiotic fills in subsequent pregnancies.

DESIGNS

A population-based drug utilisation study.

SETTING

Norwegian primary care.

PARTICIPANTS

653 058 pregnancies derived from Medical Birth Registry of Norway linked to the Norwegian Prescription Database (2006-2016).

MAIN OUTCOME MEASURE

Proportion of pregnancies exposed to antibiotics aggregated by week in pregnancy time windows.

STATISTICAL ANALYSES

We descriptively analysed antibiotic prescription fills patterns and components in pregnant women. The changes in antibiotic fills in pregnancy time windows were assessed using ITSA. Interruptions points at week 4 to week 7 into pregnancy and delivery were used. Factors associated with antibiotic fills during pregnancy were identified using generalised estimating equations for Poisson regression. Recurrent antibiotic use was estimated using proportion of women who filled antibiotic prescription in a subsequent pregnancy.

RESULTS

Antibiotics were filled in 27.6% pregnancies. The ITSA detected an immediate decrease of 0.07 percentage points (95% CI -0.13 to -0.01) in the proportion of exposed pregnancies at 4 weeks after conception, mainly among women taking folic acid before pregnancy. This proportion increased shortly after delivery (immediate change=1.61 percentage points (95% CI 0.31 to 2.91)) then decreased gradually afterwards (change in slope=-0.19 percentage points, 95% CI -0.34 to -0.05)). The strongest factor associated with antibiotic fills during pregnancy was having recurrent urinary tract infections (adjusted OR=2.65, 95% CI 2.59 to 2.72). Women who had filled antibiotics during a pregnancy were up to three times more likely to fill antibiotics in the subsequent pregnancies.

CONCLUSIONS

ITSA highlighted important impact of pregnancy and delivery on antibiotic fillings. Having antibiotic fills in a pregnancy was associated with recurrent antibiotic fills in subsequent ones.

How often will midwives and obstetricians experience obstetric emergencies or high-risk deliveries: a national cross-sectional study

OBJECTIVE

To estimate how often midwives, specialty trainees and doctors specialised in obstetrics and gynaecology are attending to specific obstetric emergencies or high-risk deliveries (obstetric events).

DESIGN

A national cross-sectional study.

SETTING

All hospital labour wards in Denmark.

PARTICIPANTS

Midwives (n=1303), specialty trainees (n=179) and doctors specialised in obstetrics and gynaecology (n=343) working in hospital labour wards (n=21) in Denmark in 2018.

METHODS

Categories of obstetric events comprised of Apgar score <7/5 min, eclampsia, emergency caesarean sections, severe postpartum haemorrhage, shoulder dystocia, umbilical cord prolapse, vaginal breech deliveries, vaginal twin deliveries and vacuum extraction. Data on number of healthcare professionals were obtained through the Danish maternity wards, the Danish Health Authority and the Danish Society of Obstetricians and Gynaecologists. We calculated the time interval between attending each obstetric event by dividing the number of events occurred with the number of healthcare professionals.

OUTCOME MEASURES

The time interval between attending a specific obstetric event.

RESULTS

The average time between experiencing obstetric events ranged from days to years. Emergency caesarean sections, which occur relatively frequent, were attended on average every other month by midwives, every 9 days for specialty trainees and every 17 days by specialist doctors. On average, rare events like eclampsia were experienced by midwives only every 42 years, every 6 years by specialty trainees and every 11 years by specialist doctors.

CONCLUSIONS

Some obstetric events occur extremely rarely, hindering the ability to obtain and maintain the clinical skills to manage them through clinical practice alone. By assessing the frequency of a healthcare professionals attending an obstetric emergency, our study contributes to assessing the need for supplementary educational initiatives and interventions to learn and maintain clinical skills.

Exposure to duloxetine during pregnancy and risk of congenital malformations and stillbirth: A nationwide cohort study in Denmark and Sweden

BACKGROUND

The prevalence of depression and the exposure to antidepressants are high among women of reproductive age and during pregnancy. Duloxetine is a selective serotonin-norepinephrine reuptake inhibitor (SNRI) approved in the United States and Europe in 2004 for the treatment of depression. Fetal safety of duloxetine is not well established. The present study evaluates the association of exposure to duloxetine during pregnancy and the risk of major and minor congenital malformations and the risk of stillbirths.

METHODS AND FINDINGS

A population-based observational study was conducted based on data from registers in Sweden and Denmark. All registered births and stillbirths in the medical birth registers between 2004 and 2016 were included. Malformation diagnoses were identified up to 1 year after birth. Logistic regression analyses were used. Potential confounding was addressed through multiple regression, propensity score (PS) matching, and sensitivity analyses. Confounder variables included sociodemographic information (income, education, age, year of birth, and country), comorbidity and comedication, previous psychiatric contacts, and birth-related information (smoking during pregnancy and previous spontaneous abortions and stillbirths). Duloxetine-exposed women were compared with 4 comparators: (1) duloxetine-nonexposed women; (2) selective serotonin reuptake inhibitor (SSRI)-exposed women; (3) venlafaxine-exposed women; and (4) women exposed to duloxetine prior to, but not during, pregnancy. Exposure was defined as redemption of a prescription during the first trimester and throughout pregnancy for the analyses of malformations and stillbirths, respectively. Outcomes were major and minor malformations and stillbirths gathered from the national patient registers. The cohorts consisted of more than 2 million births with 1,512 duloxetine-exposed pregnancies. No increased risk for major malformations, minor malformations, or stillbirth was found across comparison groups in adjusted and PS-matched analyses. Duloxetine-exposed versus duloxetine-nonexposed PS-matched analyses showed odds ratio (OR) 0.98 (95% confidence interval [CI] 0.74 to 1.30, p = 0.909) for major malformations, OR 1.09 (95% CI 0.82 to 1.45, p = 0.570) for minor malformation, and 1.18 (95% CI 0.43 to 3.19, p = 0.749) for stillbirths. For the individual malformation subtypes, some findings were statistically significant but were associated with large statistical uncertainty due to the extremely small number of events. The main limitations for the study were that the indication for duloxetine and a direct measurement of depression severity were not available to include as covariates.

CONCLUSIONS

Based on this observational register-based nationwide study with data from Sweden and Denmark, no increased risk of major or minor congenital malformations or stillbirth was associated with exposure to duloxetine during pregnancy.

Prenatal exposure to nitrofurantoin and risk of childhood leukaemia: a registry-based cohort study in four Nordic countries

Background

Studies have suggested increased risks of childhood leukaemia after prenatal exposure to antibiotics, particularly nitrofurantoin. However, these findings may be related to the underlying maternal infection. This multinational study aimed to investigate the association between prenatal nitrofurantoin exposure and childhood leukaemia while accounting for maternal infection.

Methods

In a population-based cohort study of children born in Denmark, Finland, Norway or Sweden from 1997 to 2013, prenatal exposure to nitrofurantoin or pivmecillinam (active comparator) was ascertained from national Prescription Registries. Childhood leukaemia was identified by linkage to national Cancer Registries. Poisson regression was used to estimate incidence rate ratios (IRRs) and incidence rate differences (IRDs) with inverse probability of treatment weights applied to account for confounding.

Results

We included 44 091 children prenatally exposed to nitrofurantoin and 247 306 children prenatally exposed to pivmecillinam. The children were followed for 9.3 years on average (standard deviation 4.1). There were 161 cases of childhood leukaemia. The weighted IRR for prenatal nitrofurantoin exposure when compared with pivmecillinam was 1.34 (95% confidence interval 0.88, 2.06), corresponding to an IRD of 15 per million person-years. Higher point estimates were seen for first- and third-trimester exposure. There was no evidence of a dose–response relationship.

Conclusions

Prenatal exposure to nitrofurantoin was not substantially associated with childhood leukaemia, although a slightly elevated IRR with confidence intervals including the null was observed, corresponding to a small absolute risk. The lack of a dose–response relationship and a clear biological mechanism to explain the findings suggests against a causal association.

[Insights into pregnancy and breastfeeding in inflammatory rheumatic diseases through observational data]

Information on pregnancy and breastfeeding in women with chronic inflammatory rheumatic diseases is relevant for a successful pregnancy and also for maternal and child health. In general, pregnant and breastfeeding women are excluded from randomized clinical trials and therefore evidence for clinical care and counselling has to be generated from observational studies. In the past decades, various data collections have been established for this purpose in addition to the existing spontaneous reporting systems initiated by drug authorities, with the aim of monitoring the teratogenic risk of a drug. Health insurance claims data, electronic health records and Scandinavian registers are also increasingly being used for research on pregnancy-associated events; however, all these data sources lack the inclusion of the maternal disease, especially with respect to its inflammatory component. Established cohort studies, biologics and disease registries record disease activity but are not designed for pregnancy-specific questions. Pregnancy registries and studies in rheumatology close this gap. In order to be able to make a better assessment of the possibilities and limitations of existing data sources on pregnancy and lactation, they are presented in detail in the following review including their respective advantages and disadvantages and examples from rheumatology are given. In addition, existing collaborations as well as studies for investigating the influence of paternal rheumatic disease are highlighted.

Cardiovascular disease, obesity, and type 2 diabetes in children born after assisted reproductive technology: A population-based cohort study

BACKGROUND

Some earlier studies have found indications of significant changes in cardiometabolic risk factors in children born after assisted reproductive technology (ART). Most of these studies are based on small cohorts with high risk of selection bias. In this study, we compared the risk of cardiovascular disease, obesity, and type 2 diabetes between singleton children born after ART and singleton children born after spontaneous conception (SC).

METHODS AND FINDINGS

This was a large population-based cohort study of individuals born in Norway, Sweden, Finland, and Denmark between 1984 and 2015. Data were obtained from national ART and medical birth registers and cross-linked with data from national patient registers and other population-based registers in the respective countries. In total, 122,429 children born after ART and 7,574,685 children born after SC were included. Mean (SD) maternal age was 33.9 (4.3) years for ART and 29.7 (5.2) for SC, 67.7% versus 41.8% were primiparous, and 45.2% versus 32.1% had more than 12 years of education. Preterm birth (<37 weeks 0 days) occurred in 7.9% of children born after ART and 4.8% in children born after SC, and 5.7% versus 3.3% had a low birth weight (<2,500 g). Mean (SD) follow-up time was 8.6 (6.2) years for children born after ART and 14.0 (8.6) years for children born after SC. In total, 135 (0.11%), 645 (0.65%), and 18 (0.01%) children born after ART were diagnosed with cardiovascular disease (ischemic heart disease, cardiomyopathy, heart failure, or cerebrovascular disease), obesity or type 2 diabetes, respectively. The corresponding values were 10,702 (0.14%), 30,308 (0.74%), and 2,919 (0.04%) for children born after SC. In the unadjusted analysis, children born after ART had a significantly higher risk of any cardiovascular disease (hazard ratio [HR] 1.24; 95% CI 1.04-1.48; p = 0.02), obesity (HR 1.13; 95% CI 1.05-1.23; p = 0.002), and type 2 diabetes (HR 1.71; 95% CI 1.08-2.73; p = 0.02). After adjustment, there was no significant difference between children born after ART and children born after SC for any cardiovascular disease (adjusted HR [aHR]1.02; 95% CI 0.86-1.22; p = 0.80) or type 2 diabetes (aHR 1.31; 95% CI 0.82-2.09; p = 0.25). For any cardiovascular disease, the 95% CI was reasonably narrow, excluding effects of a substantial magnitude, while the 95% CI for type 2 diabetes was wide, not excluding clinically meaningful effects. For obesity, there was a small but significant increased risk among children born after ART (aHR 1.14; 95% CI 1.06-1.23; p = 0.001). Important limitations of the study were the relatively short follow-up time, the limited number of events for some outcomes, and that the outcome obesity is often not considered as a disease and therefore not caught by registers, likely leading to an underestimation of obesity in both children born after ART and children born after SC.

CONCLUSIONS

In this study, we observed no difference in the risk of cardiovascular disease or type 2 diabetes between children born after ART and children born after SC. For obesity, there was a small but significant increased risk for children born after ART.

TRIAL REGISTRATION NUMBER

ISRCTN11780826.

Nordic Health Registry-Based Research: A Review of Health Care Systems and Key Registries

The Nordic countries are Denmark, Finland, Iceland, Norway, and Sweden and comprise a total population of approximately 27 million. The countries provide unique opportunities for joint health registry-based research in large populations with long and complete follow-up, facilitated by shared features, such as the tax-funded and public health care systems, the similar population-based registries, and the personal identity number as unique identifier of all citizens. In this review, we provide an introduction to the health care systems, key registries, and how to navigate the practical and ethical aspects of setting up such studies. For each country, we provide an overview of population statistics and health care expenditures, and describe the operational and administrative organization of the health care system. The Nordic registries provide population-based, routine, and prospective data on individuals lives and health with virtually complete follow-up and exact censoring information. We briefly describe the total population registries, birth registries, patient registries, cancer registries, prescription registries, and causes of death registries with a focus on period of coverage, selected key variables, and potential limitations. Lastly, we discuss some practical and legal perspectives. The potential of joint research is not fully exploited, mainly due to legal and practical difficulties in, for example, cross-border sharing of data. Future tasks include clear and transparent legal pathways and a framework by which practical aspects are facilitated.

Maternal childbirth experience and time of delivery: a retrospective 7-year cohort study of 105 847 parturients in Finland

OBJECTIVES

To explore how the time of delivery influences childbirth experience.

DESIGN

A retrospective cohort study.

SETTING

Childbirth in the four Helsinki and Uusimaa Hospital District hospitals, Finland, from 2012 to 2018.

PARTICIPANTS

105 847 childbirths with a singleton live fetus.

MAIN OUTCOME MEASURES

Childbirth experience measured by Visual Analogue Scale (VAS).

RESULTS

The major difference in average childbirth experience measured by VAS was between primiparas (8.03; 95% CI 8.01 to 8.04) and multiparas (8.47; 95% CI 8.45 to 8.48). Risk ratio (RR) of the low VAS (≤5) was 2.3 when primiparas were compared with multiparas. Differences in VAS between distinct periods were found in two stages: annual and time of day. The decrease in VAS from 2012-2016 to 2017-2018 in primiparas was from 7.97 (95% CI 7.95 to 7.99) to 7.80 (95% CI 7.77 to 7.83) and from 2014-2016 to 2017-2018 in multiparas from 8.60 (95% CI 8.58 to 8.61) to 8.49 (95% CI 8.47 to 8.52). Corresponding RRs of low VAS were 1.3 for primiparas and 1.2 for multiparas. Hourly differences in VAS were detected in primiparas between office hours 08:00-15:59 (7.97; 95% CI 7.94 to 7.99) and other times (night 00:00-07:59; 7.91; 95% CI 7.88 to 7.94; and evening 16:00-23:59; 7.90; 95% CI 7.87 to 7.92). In multiparas differences in VAS were detected between evening (8.52; 95% CI 8.50 to 8.54) and other periods (night; 8.56; 95% CI 8.54 to 9.58; and office hours; 8.57; 95% CI 8.55 to 8.59).

CONCLUSION

The maternal childbirth experience depended on the time of delivery. Giving birth during the evening led to impaired childbirth experience in both primiparas and multiparas, compared with delivery at other times. The impact of labour induction on childbirth experience should be further examined. The reorganisation of delivery services and the reduction of birth preparations might affect annual VAS. VAS is a simple method of measuring the complex entity of childbirth experience, and our results indicate its ability to capture temporal variation.

Duloxetine Exposure During Pregnancy and the Risk of Spontaneous and Elective Abortion: A Danish Nationwide Observational Study

BACKGROUND

Depression and antidepressant treatment are widespread among women of childbearing age.

OBJECTIVE

This study evaluates the association between duloxetine exposure during pregnancy and spontaneous and elective abortions.

PATIENTS AND METHODS

The nationwide, observational study based on register data from Denmark included women with a recorded pregnancy in the birth register or an abortion in the patient register between 2004 and 2016. Duloxetine-exposed women were compared with (1) duloxetine non-exposed, (2) selective serotonin reuptake inhibitor (SSRI)-exposed, (3) venlafaxine-exposed, and (4) women discontinuing duloxetine before pregnancy. Exposure status was based on records of redeemed prescriptions. Cox regression with adjustments and propensity score matching was applied.

RESULTS

The data from 1,019,957 pregnancies were used, including 1,212 pregnancies exposed to duloxetine. Duloxetine-exposed women had an increased hazard ratio (HR) for spontaneous abortions compared with SSRI-exposed women: propensity score matched HR 1.25 [95% confidence interval (CI), 1.00-1.57]. No increased hazard was observed for duloxetine-exposed women compared with duloxetine non-exposed: 1.08 (95% CI 0.89-1.31); venlafaxine-exposed: 1.08 (95% CI 0.82-1.41); and duloxetine discontinuers: 0.99 (95% CI 0.76-1.30). An increased HR of elective abortions was observed in duloxetine-exposed women compared to duloxetine non-exposed: 1.41 (95% CI 1.25-1.59); SSRI-exposed: 1.32 (95% CI 1.15-1.51); and duloxetine discontinuers: 1.46 (95% CI 1.23-1.75), but not to venlafaxine-exposed women: 1.09 (95% CI 0.93-1.27).

CONCLUSION

There was no increased risk of spontaneous or elective abortion associated with exposure to duloxetine. The increase risk observed for women exposed to duloxetine in comparison with SSRI-exposed for spontaneous and in comparison with all groups (except venlafaxine-exposed) for elective abortion suggested confounding.

Maternal diseases and risk of hypertensive disorders of pregnancy across gestational age groups

OBJECTIVES

To estimate the risk of hypertensive disorders of pregnancy in nulliparous women with diabetes, chronic hypertension or obesity in three gestational age groups.

STUDY DESIGN

Population-based observational cohort study of 382 618 nulliparous women (94 280 with known BMI) using Medical Birth Registry of Norway and Statistics Norway. Main exposure variables were diabetes, chronic hypertension, Body Mass Index (BMI). Multiple regression analysis was performed without (model 1) and with (model 2) BMI.

MAIN OUTCOME MEASURES

Preeclampsia stratified by gestational age group at delivery: early (23⁰-33⁶ weeks), intermediate (34⁰-36⁶ weeks) and late (37⁰-43⁶ weeks), and gestational hypertension.

RESULTS

In model 1, Type 1 diabetes was associated with early (aOR = 5.0, 95%CI 3.8, 6.7), intermediate (aOR = 10.2, 95%CI 8.5, 12.3) and late preeclampsia (aOR = 2.7, 95%CI 2.4, 3.2), compared to no diabetes. Compared to normotensive women, women with chronic hypertension had an increased risk of preeclampsia in all groups: early (aOR = 8.68, 95%CI 6.94, 10.85), intermediate (aOR = 5.59, 95%CI 4.46, 7.02), late (aOR = 3.45, 95%CI 3.00, 3.96). The same trends persisted after adjusting for BMI (model 2). Obesity remained an independent risk factor for hypertensive disorders of pregnancy.

CONCLUSIONS

Maternal diabetes, chronic hypertension and obesity were associated with an increased risk of hypertensive disorders of pregnancy across all gestational age groups in nulliparous women. Adjusting for BMI did not further modify the risk in these women, although 75% of the women in the study lacked BMI data.

The data we have: Pregnancy and birth related data collection in Australia, Canada, Europe and the USA - A web-based survey of practice

Objectives

To determine the feasibility of combining routinely recorded perinatal data from several databases in high-income countries to assess the risk of recurrent stillbirth.

Methods

Web-based questionnaire survey with reminder emails and searching of relevant country websites.

Results

120 countries/regions in Canada, Europe and the USA were invited to participate and 83 (69%) responded. Of those one had no data, and two did not wish to take part. The remaining 80 were sent the questionnaire and 63 (53%) were completed. Twenty-seven countries/regions reported that they collect information on all perinatal events (including early pregnancy loss), 34 on live births and stillbirths and two only live births (stillbirths recorded in a separate database). Most countries (53/63) can link two or more pregnancies occurring in the same woman. Data and information extracted from the Australian and New Zealand Government websites showed that information on all perinatal events is collected nationally in New Zealand and in 5/8 regions in Australia. Both Australia and New Zealand can link two or more pregnancies occurring in the same woman. Maternal age and caffeine consumption were the most and least consistently collected demographic indicators respectively. Diabetes mellitus and mental health problems, birthweight and obstetric cholestasis the most and least consistently collected for medical conditions and pregnancy condition/complications. Procedures for gaining access to data vary between countries.

Conclusion

This study demonstrates that it is possible to link pregnancies in the same woman to assess the risk of recurrent stillbirth using routinely collected perinatal data in all states/territories in Australia, 7/8 responding provinces/territories in Canada, 21/27 responding countries/regions in Europe, New Zealand and 26/28 responding states in the USA. The scope of the databases and quality and extent of data collected (thus their potential use) varied, as did procedures for accessing their data.

Association between maternal country of birth and preterm birth: A population-based register study of 910,752 deliveries

Aims: The aim of this study was to analyse associations between maternal country of birth and preterm birth among women giving birth in Norway. Methods: A population-based register study was conducted employing official national databases in Norway. All singleton births, with neonates without major anomalies, between 1999 and 2014 were included (N=910,752). We estimated odds ratios (ORs) for extremely preterm birth (<28 weeks gestation), very preterm birth (28–33 weeks gestation) and late preterm birth (34–36 weeks gestation) by maternal country of birth. We conducted multivariable regression analyses, adjusting for maternal, obstetric and socio-economic confounders. Results: For extremely preterm births (0.4% of the study population), women with an unknown country of birth (adjusted OR (aOR)=3.09; 95% confidence interval (CI) 2.26–4.22) and women born in sub-Saharan Africa (aOR=1.66; CI 1.40–1.96) had the highest ORs compared to Norwegian-born women. For very preterm births (1.2% of the study population), women with an unknown country of birth (aOR=1.72; CI 1.36–2.18) and women born in South Asia (aOR=1.48; CI 1.31–1.66) had the highest ORs. For late preterm births (3.8% of the study population), women born in East Asia Pacific/Oceania (aOR=1.33; CI 1.25–1.41) and South Asia (aOR=1.30; CI 1.21–1.39) had the highest ORs. Conclusions: After adjusting for maternal, obstetric and socio-economic risk factors, maternal country of birth remained significantly associated with preterm birth. Women with an unknown country of birth and women born in sub-Saharan Africa were found to be at increased risk of extremely preterm birth.

Maternal health, in-utero, and perinatal exposures and risk of thyroid cancer in offspring: a Nordic population-based nested case-control study

BACKGROUND

Thyroid cancer tends to be diagnosed at a younger age (median age 51 years) compared with most other malignancies (such as breast cancer [62 years] or lung cancer [71 years]). The incidence of thyroid cancer is higher in women than men diagnosed from early adolescence. However, few in-utero and early life risk exposures associated with increased risk of thyroid cancer have been identified.

METHODS

In this population-based nested case-control study we used registry data from four Nordic countries to assess thyroid cancer risk in offspring in relation to maternal medical history, pregnancy complications, and birth characteristics. Patient with thyroid cancer (cases) were individuals born and subsequently diagnosed with first primary thyroid cancer from 1973 to 2013 in Denmark, 1987 to 2014 in Finland, 1967 to 2015 in Norway, or 1973 to 2014 in Sweden. Each case was matched with up to ten individuals without thyroid cancer (controls) based on birth year, sex, country, and county of birth. Cases and matched controls with a previous diagnosis of any cancer, other than non-melanoma skin cancer, at the time of thyroid cancer diagnosis were excluded. Cases and matched controls had to reside in the country of birth at the time of thyroid cancer diagnosis. Conditional logistic regression models were used to calculate odds ratios (ORs) with 95% CIs.

RESULTS

Of the 2437 cases, 1967 (81·4%) had papillary carcinomas, 1880 (77·1%) were women, and 1384 (56·7%) were diagnosed before age 30 years (range 0-48). Higher birth weight (OR per kg 1·14 [95% CI 1·05-1·23]) and congenital hypothyroidism (4·55 [1·58-13·08]); maternal diabetes before pregnancy (OR 1·69 [0·98-2·93]) and postpartum haemorrhage (OR 1·28 [1·06-1·55]); and (from registry data in Denmark) maternal hypothyroidism (18·12 [10·52-31·20]), hyperthyroidism (11·91 [6·77-20·94]), goiter (67·36 [39·89-113·76]), and benign thyroid neoplasms (22·50 [6·93-73·06]) were each associated with an increased risk of thyroid cancer in offspring.

INTERPRETATION

In-utero exposures, particularly those related to maternal thyroid disorders, might have a long-term influence on thyroid cancer risk in offspring.

FUNDING

Intramural Research Program of the National Cancer Institute (National Institutes of Health).

Fear of childbirth after medical vs surgical abortion. Population-based register study from Finland

INTRODUCTION

To evaluate the effect of method of induced abortion and other abortion-associated variables on the incidence of fear of childbirth in subsequent pregnancy.

MATERIAL AND METHODS

This population-based register study cohort includes all nulliparous women with their first pregnancy ending in an induced abortion in 2000-2015 and subsequent pregnancy with live singleton delivery between 2000 and 2017 (n = 21 479). Data were derived from three national registers maintained by the Finnish Institute for Health and Welfare. We divided the study population in three cohorts: (a) medical and (b) surgical abortion during first trimester (≤84 days of gestation), and (c) medical abortion during second trimester (85-168 days of gestation). Primary outcome measures were the incidence of registry-identified fear of childbirth and cesarean delivery related to it.

RESULTS

The overall incidence of fear of childbirth was 5.6% (n = 1209). Altogether, 19.2% (n = 4121) of women underwent cesarean delivery. The odds were elevated especially for elective cesarean delivery (odds ratio [OR] 9.30, 95% CI 7.95-10.88, P < .001) in women with fear of childbirth. In multivariable analysis, the odds for fear of childbirth (adjusted OR [aOR] 0.80, 95% CI 0.68-0.94) and cesarean delivery (aOR 0.66, 95% CI 0.84-0.90) were decreased in women with a history of first-trimester medical abortion compared with those with first-trimester surgical abortion. Second-trimester medical abortion had no effect on the odds for fear of childbirth (aOR 1.04, 95% CI 0.71-1.50). Maternal age of 30-39 years and interpregnancy interval over 2 years were additional risk factors for both fear of childbirth and cesarean delivery, but surgical evacuation of uterus after the abortion was not.

CONCLUSIONS

One first- or second-trimester medical abortion does not increase the odds for fear of childbirth, and cesarean delivery related to it in subsequent pregnancy when compared with first-trimester surgical abortion. Older maternal age and longer interpregnancy interval emerged as risk factors for fear of childbirth.

Mortality Among Young Adults Born Preterm and Early Term in 4 Nordic Nations

IMPORTANCE

Adverse long-term outcomes in individuals born before full gestation are not confined to individuals born at extreme gestational ages. Little is known regarding mortality patterns among individuals born in the weeks close to ideal gestation, and the exact causes are not well understood; both of these are crucial for public health, with the potential for modification of risk.

OBJECTIVE

To examine the risk of all-cause and noncommunicable diseases (NCD) deaths among young adults born preterm and early term.

DESIGN, SETTING, AND PARTICIPANTS

This multinational population-based cohort study used nationwide birth cohorts from Norway, Sweden, Denmark, and Finland for individuals born between 1967 and 2002. Individuals identified at birth who had not died or emigrated were followed up for mortality from age 15 years to 2017. Analyses were performed from June 2019 to May 2020.

EXPOSURES

Categories of gestational age (ie, moderate preterm birth and earlier [23-33 weeks], late preterm [34-36 weeks], early term [37-38 weeks], full term [39-41 weeks] and post term [42-44 weeks]).

MAIN OUTCOMES AND MEASURES

All-cause mortality and cause-specific mortality from NCD, defined as cancer, diabetes, chronic lung disease, and cardiovascular disease (CVD).

RESULTS

A total of 6 263 286 individuals were followed up for mortality from age 15 years. Overall, 339 403 (5.4%) were born preterm, and 3 049 100 (48.7%) were women. Compared with full-term birth, the adjusted hazard ratios (aHRs) for all-cause mortality were 1.44 (95% CI, 1.34-1.55) for moderate preterm birth and earlier; 1.23 (95% CI, 1.18-1.29) for late preterm birth; and 1.12 (95% CI, 1.09-1.15) for early-term birth. The association between gestational age and all-cause mortality were stronger in women than in men (P for interaction = .03). Preterm birth was associated with 2-fold increased risks of death from CVD (aHR, 1.89; 95% CI, 1.45-2.47), diabetes (aHR, 1.98; 95% CI, 1.44-2.73), and chronic lung disease (aHR, 2.28; 95% CI, 1.36-3.82). The main associations were replicated across countries and could not be explained by familial or individual confounding factors.

CONCLUSIONS AND RELEVANCE

The findings of this study strengthen the evidence of increased risk of death from NCDs in young adults born preterm. Importantly, the increased death risk was found across gestational ages up to the ideal term date and includes the much larger group with early-term birth. Excess mortality associated with shorter gestational age was most pronounced for CVDs, chronic lung disease, and diabetes.

Congenital Malformations in Denmark: Considerations for the Use of Danish Health Care Registries

BACKGROUND

Danish health registers are used widely to examine associations between specific risk factors and congenital malformations. Various overall prevalence rates of malformations have been reported in Denmark indicating differences in the underlying data sources or malformation definitions. We described trends in registration of malformations in Denmark 1997-2017 and identified potential caveats for the use of Danish health registries in epidemiological studies. We composed a Danish adaptation of EUROCATs definition of malformations.

METHODS

Using nationwide Danish health registries, we identified all recorded pregnancies and followed livebirths for up to 5 years. We described the different data sources, ways to identify malformations, the overall rate of malformations over time, and identified the 10 most common major malformations.

RESULTS

A total of 1,340,774 foetuses and infants from 1,313,281 pregnancies among 747,144 women from 1997 to 2017 were analysed. Using primary and secondary diagnoses from all available sources and restricting hip malformations to diagnoses after 6 weeks postpartum, we found that 65,411 (49/1000) foetuses or infants had at least one major malformation defined by our Danish translation of EUROCATs definition of malformations. The prevalence of major malformations increased over time from 39/1000 in 1997 to 53/1000 in 2017. The most common specific malformations were malformations of cardiac septa (Q21) and great arteries (Q25) with a peak of 10 and 6/1000 births in 2010 and 2009, respectively.

CONCLUSION

Malformations should be identified using primary and secondary diagnoses from the Birth register, the Patient register, and the Cause of Death register. To increase transparency and external validity, classification of major malformations should be based on the Danish adaptation of EUROCATs classification of malformations.

Cancer risk in individuals with major birth defects: large Nordic population based case-control study among children, adolescents, and adults

OBJECTIVE

To examine associations between birth defects and cancer from birth into adulthood.

DESIGN

Population based nested case-control study.

SETTING

Nationwide health registries in Denmark, Finland, Norway, and Sweden.

PARTICIPANTS

62 295 cancer cases (0-46 years) and 724 542 frequency matched controls (matched on country and birth year), born between 1967 and 2014.

MAIN OUTCOME MEASURES

Relative risk of cancer in relation to major birth defects, estimated as odds ratios with 99% confidence intervals from logistic regression models.

RESULTS

Altogether, 3.5% (2160/62 295) of cases and 2.2% (15 826/724 542) of controls were born with major birth defects. The odds ratio of cancer for people with major birth defects compared with those without was 1.74 (99% confidence interval 1.63 to 1.84). For individuals with non-chromosomal birth defects, the odds ratio of cancer was 1.54 (1.44 to 1.64); for those with chromosomal anomalies, the odds ratio was 5.53 (4.67 to 6.54). Many structural birth defects were associated with later cancer in the same organ system or anatomical location, such as defects of the eye, nervous system, and urinary organs. The odds ratio of cancer increased with number of defects and decreased with age, for both non-chromosomal and chromosomal anomalies. The odds ratio of cancer in people with any non-chromosomal birth defect was lower in adults (≥20 years: 1.21, 1.09 to 1.33) than in adolescents (15-19 years: 1.58, 1.31 to 1.90) and children (0-14 years: 2.03, 1.85 to 2.23). The relative overall cancer risk among adults with chromosomal anomalies was markedly reduced from 11.3 (9.35 to 13.8) in children to 1.50 (1.01 to 2.24). Among adults, skeletal dysplasia (odds ratio 3.54, 1.54 to 8.15), nervous system defects (1.76, 1.16 to 2.65), chromosomal anomalies (1.50, 1.01 to 2.24), genital organs defects (1.43, 1.14 to 1.78), and congenital heart defects (1.28, 1.02 to 1.59) were associated with overall cancer risk.

CONCLUSIONS

The increased risk of cancer in individuals with birth defects persisted into adulthood, both for non-chromosomal and chromosomal anomalies. Further studies on the molecular mechanisms involved are warranted.

Fertility treatment and oral contraceptive discontinuation for identification of pregnancy planning in routinely collected health data - an application to analgesic and antibiotic utilisation

BACKGROUND

Women with unplanned pregnancies use folic acid less frequently, and more often use potentially teratogenic medications in the first trimester. Yet most studies based on routinely collected data lack information on pregnancy planning. Further, only pregnancies proceeding beyond a certain gestational age appear in routinely collected data, creating the possibility for collider-stratification bias. If pregnancy intention could be identified, pregnancies could be ascertained earlier. This study aimed to investigate fertility treatment and discontinuation of oral contraception (OC) as proxies for pregnancy planning by describing variations in patterns of prescription fills for antibiotics and analgesics during the peri-pregnancy period by these proxies of pregnancy intention.

METHODS

Fertility treatment with clomiphene and discontinuation of OC were identified in the Norwegian Prescription Database (NorPD) and linked with data from the Medical Birth Registry of Norway for the years 2006 to 2017. Filled prescriptions for antibiotics and analgesics from NorPD were displayed for women on fertility treatment, women who discontinued OC before pregnancy, and women who discontinued during pregnancy.

RESULTS

Of 172,585 included pregnancies, fertility treatment was identified in 19,449, and OC discontinuation before or during pregnancy in 153,136. Women who discontinued OC during pregnancy were less likely to use preconception folic acid (25.4%) than women who discontinued before pregnancy (32.9%), and women on fertility treatment (51.0%). Proportions of first trimester prescription fills were 4.9% (analgesics) and 12.8% (antibiotics) for women who discontinued OC during pregnancy, compared to 4.0 and 11.4% in women who discontinued OC before pregnancy, and 4.7 and 11.0% in women on fertility treatment.

CONCLUSIONS

There were no substantial differences in patterns of prescription fills for analgesics and antibiotics before or during pregnancy by fertility treatment and OC discontinuation. This suggests that there were few differences in medication use between women with planned and unplanned pregnancies, or that fertility treatment and timing of OC discontinuation from routinely collected health data cannot stand alone in the identification of unplanned pregnancies. A narrower definition of OC discontinuation during pregnancy seemed to be a better proxy, but this should be confirmed in other studies.