Examining Nonparticipation in the Maternal Follow-up Within the Danish National Birth Cohort

Lifetime history of gestational diabetes and cognitive function in parous women in midlife

AIMS/HYPOTHESIS

We aimed to determine whether a history of gestational diabetes mellitus (GDM) is associated with cognitive function in midlife.

METHODS

We conducted a secondary data analysis of the prospective Nurses' Health Study II. From 1989 to 2001, and then in 2009, participants reported their history of GDM. A subset participated in a cognition sub-study in 2014-2019 (wave 1) or 2018-2022 (wave 2). We included 15,906 parous participants (≥1 birth at ≥18 years) who completed a cognitive assessment and were free of CVD, cancer and diabetes before their first birth. The primary exposure was a history of GDM. Additionally, we studied exposure to GDM and subsequent type 2 diabetes mellitus (neither GDM nor type 2 diabetes, GDM only, type 2 diabetes only or GDM followed by type 2 diabetes) and conducted mediation analysis by type 2 diabetes. The outcomes were composite z scores measuring psychomotor speed/attention, learning/working memory and global cognition obtained with the Cogstate brief battery. Mean differences (β and 95% CI) in cognitive function by GDM were estimated using linear regression.

RESULTS

The 15,906 participants were a mean of 62.0 years (SD 4.9) at cognitive assessment, and 4.7% (n=749) had a history of GDM. In models adjusted for age at cognitive assessment, race and ethnicity, education, wave of enrolment in the cognition sub-study, socioeconomic status and pre-pregnancy characteristics, women with a history of GDM had lower performance in psychomotor speed/attention (β -0.08; 95% CI -0.14, -0.01) and global cognition (β -0.06; 95% CI -0.11, -0.01) than those without a history of GDM. The lower cognitive performance in women with GDM was only partially explained by the development of type 2 diabetes.

CONCLUSIONS/INTERPRETATION

Women with a history of GDM had poorer cognition than those without GDM. If replicated, our findings support future research on early risk modification strategies for women with a history of GDM as a potential avenue to decrease their risk of cognitive impairment.

Inverse probability weighting for self-selection bias correction in the investigation of social inequality in mortality

BACKGROUND

Empirical evaluation of inverse probability weighting (IPW) for self-selection bias correction is inaccessible without the full source population. We aimed to: (i) investigate how self-selection biases frequency and association measures and (ii) assess self-selection bias correction using IPW in a cohort with register linkage.

METHODS

The source population included 17 936 individuals invited to the Copenhagen Aging and Midlife Biobank during 2009-11 (ages 49-63 years). Participants counted 7185 (40.1%). Register data were obtained for every invited person from 7 years before invitation to the end of 2020. The association between education and mortality was estimated using Cox regression models among participants, IPW participants and the source population.

RESULTS

Participants had higher socioeconomic position and fewer hospital contacts before baseline than the source population. Frequency measures of participants approached those of the source population after IPW. Compared with primary/lower secondary education, upper secondary, short tertiary, bachelor and master/doctoral were associated with reduced risk of death among participants (adjusted hazard ratio [95% CI]: 0.60 [0.46; 0.77], 0.68 [0.42; 1.11], 0.37 [0.25; 0.54], 0.28 [0.18; 0.46], respectively). IPW changed the estimates marginally (0.59 [0.45; 0.77], 0.57 [0.34; 0.93], 0.34 [0.23; 0.50], 0.24 [0.15; 0.39]) but not only towards those of the source population (0.57 [0.51; 0.64], 0.43 [0.32; 0.60], 0.38 [0.32; 0.47], 0.22 [0.16; 0.29]).

CONCLUSIONS

Frequency measures of study participants may not reflect the source population in the presence of self-selection, but the impact on association measures can be limited. IPW may be useful for (self-)selection bias correction, but the returned results can still reflect residual or other biases and random errors.

Mode of birth and long-term maternal mental health: A follow-up study in the Danish National Birth Cohort

BACKGROUND

Cesarean birth has been associated with increased risks of short-term mental health problems. Little is known about whether these associations persist in the long term. This study aimed to estimate the associations between mode of birth and maternal mental health in midlife while considering mental health before and during pregnancy.

METHODS

Cohort study among mothers in the Danish National Birth Cohort. Birth mode for each woman's entire reproductive history was obtained from Danish national registries. Symptoms of depression and stress in midlife were self-reported using validated scales. Log binomial regression was used to calculate risk ratios (RR) with 95% confidence intervals (CI) for the association between birth mode and depressive symptoms. Linear regression was used to calculate mean difference in stress score by birth mode.

RESULTS

Among 42,872 women, 15.5% reported depressive symptoms at follow-up, where they were, on average, 43.9 years and 11.2 years after their last birth. Compared with women who only ever had spontaneous vaginal births, women who only had cesarean births, or had both cesarean and vaginal births with the last birth by cesarean, reported slightly more symptoms of depression (RR 1.10, 95% CI 1.01;1.20) and stress (mean difference 0.68 on a 100-point scale, 95% CI 0.10;1.26).

CONCLUSION

Whether due to the birth experience or underlying factors, depression and stress in midlife were more frequent in women with only cesarean births or whose last birth was by cesarean compared with women with vaginal births.

Reproductive history of parous women and urinary incontinence in midlife: A National Birth Cohort follow-up study

OBJECTIVE

To investigate how reproductive history was associated with urinary incontinence in midlife.

DESIGN

A follow-up study.

SETTING

Denmark.

POPULATION

A total of 39 977 mothers who participated in the Maternal Follow up (2013-2014) in the Danish National Birth Cohort. National registries provided their reproductive history.

METHODS

How parity, mode of birth and obstetric tears associated with urinary incontinence were estimated with adjusted odds ratios (OR) and 95% CI using logistic regression.

MAIN OUTCOME MEASURES

Self-reported urinary incontinence including subtypes stress, urge and mixed urinary incontinence.

RESULTS

At an average age of 44 years, the prevalence of any urinary incontinence was 32% (21% stress, 2% urge, and 8% mixed urinary incontinence). Women with two births more often had urinary incontinence than women with one birth (OR 1.20, 95% CI 1.10-1.31). Compared with women with only spontaneous births, a history of only caesarean sections was associated with much lower odds of urinary incontinence (OR 0.39, 95% CI 0.35-0.42) and a history of instrumental births with slightly lower odds (OR 0.92, 95% CI 0.86-0.98). Compared with no tear/first-degree tear as the largest tear, episiotomy was associated with less urinary incontinence (OR 0.91, 95% CI 0.86-0.97) whereas third/fourth-degree tears were associated with more (OR 1.14, 95% CI 1.04-1.25). Findings were mainly explained by similar associations with stress and mixed urinary incontinence.

CONCLUSIONS

Vaginal birth was associated with a higher risk of long-term urinary incontinence, but our results indicate that this risk may be reduced by shortening the second stage of birth.

Attention-deficit hyperactivity disorder symptoms and brain morphology: Addressing potential selection bias with inverse probability weighting

The goal of this study was to examine what happens to established associations between attention deficit hyperactivity disorder (ADHD) symptoms and cortical surface and thickness regions once we apply inverse probability of censoring weighting (IPCW) to address potential selection bias. Moreover, we illustrate how different factors that predict participation contribute to potential selection bias. Participants were 9- to 11-year-old children from the Generation R study (N = 2707). Cortical area and thickness were measured with magnetic resonance imaging (MRI) and ADHD symptoms with the Child Behavior Checklist. We examined how associations between ADHD symptoms and brain morphology change when we weight our sample back to either follow-up (ages 9-11), baseline (cohort at birth), or eligible (population of Rotterdam at time of recruitment). Weights were derived using IPCW or raking and missing predictors of participation used to estimate weights were imputed. Weighting analyses to baseline and eligible increased beta coefficients for the middle temporal gyrus surface area, as well as fusiform gyrus cortical thickness. Alternatively, the beta coefficient for the rostral anterior cingulate decreased. Removing one group of variables used for estimating weights resulted in the weighted regression coefficient moving closer to the unweighted regression coefficient. In addition, we found considerably different beta coefficients for most surface area regions and all thickness measures when we did not impute missing covariate data. Our findings highlight the importance of using inverse probability weighting (IPW) in the neuroimaging field, especially in the context of mental health-related research. We found that including all variables related to exposure-outcome in the IPW model and combining IPW with multiple imputations can help reduce bias. We encourage future psychiatric neuroimaging studies to define their target population, collect information on eligible but not included participants and use inverse probability of censoring weighting (IPCW) to reduce selection bias.

Urinary Incontinence in Midlife According to Weight Changes Across and After Childbearing Years

INTRODUCTION AND HYPOTHESIS

The objective was to investigate how weight change across and after the childbearing years was associated with urinary incontinence (UI) in midlife.

METHODS

Data were obtained from 35,645 women responding to the Maternal Follow-up questionnaire in the Danish National Birth Cohort in 2013-2014. Outcome was self-reported UI and its subtypes. Exposures were changes in body mass index (BMI) across and after the childbearing years. Adjusted odds ratios were estimated using logistic regression.

RESULTS

At follow-up, the mean age was 44 years and 32% experienced UI. Compared with stable weight, weight gain across the childbearing years of > 1 to 3, > 3 to 5 or > 5 BMI units increased the odds of any UI by 15%, 27%, and 41% respectively. For mixed UI, the odds increased by 23%, 41%, and 68% in these groups. Weight gain after childbearing showed the same pattern, but with a higher increase in the odds of mixed UI (25%, 60%, and 95% in the respective groups). Women with any weight loss during this period had 9% lower odds of any UI than women with a stable weight.

CONCLUSIONS

Weight gain across and after childbearing increased the risk of UI in midlife, especially the subtype mixed UI. Weight loss after childbearing decreased the risk.

Early-Life Exposure to Perfluoroalkyl Substances (PFAS) and Child Language and Communication Development: A Systematic Review

Language development starts during the fetal period when the brain is sensitive to endocrine disruptions from environmental contaminants. This systematic review aims to systematically summarize the existing literature on early-life exposure to PFAS and children's language and communication development, which is an indicator of neurocognitive development. A structured literature search was conducted using three databases, PubMed, Scopus, and CINAHL, last updated in April 2023. The population was defined as children and young adults. PFAS exposure was assessed pre- or postnatally. The outcome was defined as a language and communication ability assessed with validated instruments, parental self-reports, or clinical language disorder diagnoses. In total, 15 studies were identified for subsequent analyses. Thirteen were performed in background-exposed populations and two in highly exposed populations. There were some indications of potential adverse effects; however, these were not consistent across child sex, age of assessment, or PFAS exposure levels. No systematic effect of early-life PFAS exposure on language and communication development was found. These inconclusive findings may partly be explained by the use of general test instruments with limited validity as to children's language and communication development. Further studies over a wider exposure range using specific language test instruments are needed.

A critical examination of Danish norms for the Strengths and Difficulties Questionnaire (SDQ)

OBJECTIVE

The objective was to describe observed differences between the official Danish Strengths and Difficulties Questionnaire (SDQ)-norms and data from a sample based on the Danish National Birth Cohort (DNBC) including children born between 1996 and 2003. We compared the risk classification, cut-off bandings and the group sizes between the Danish norms and the values found in our sample at ages 7, 11 and 18 years.

RESULTS

Two sets of norms are used in Denmark: Arnfred's norms, based on a sample from one single Danish municipality and Niclasen's norms, based on multiple Danish cohorts, including the DNBC. Inconsistencies were found between banding scores in the two existing norms and the banding scores identified in our sample from DNBC: discrepancies included banding scores for several of the problem scales for children and preadolescents. For adolescents, we found less apparent inconsistencies between Arnfred's sample and the DNBC. Results demonstrate that the existing SDQ norms do not apply well to a large-scale cohort sample in Denmark. The usefulness of the SDQ as a screening instrument for mental health problems depends on appropriate norms. We therefore urge that the current Danish SDQ norms are used with caution, and preferably they should be revised.

Body mass index, waist circumference, and urinary incontinence in midlife: A follow-up of mothers in the Danish National Birth Cohort

BACKGROUND

Obesity is a modifiable risk factor for urinary incontinence, yet few studies have investigated how waist circumference as compared to body mass index (BMI) influences the risk of urinary incontinence.

OBJECTIVE

To estimate how BMI and waist circumference associates with risk of urinary incontinence in midlife and determine which of the two is the strongest predictor of urinary incontinence.

METHODS

Cohort study among mothers in the Danish National Birth Cohort. Weight and waist circumference were self-reported 7 years after cohort entry. Symptoms of urinary incontinence in midlife were self-reported using the International Consultation on Incontinence Questionnaire Female Lower Urinary Tract Symptoms (ICIQ-FLUTS) and analyzed continuously and as presence or absence of any, stress (SUI), urgency (UUI), and mixed (MUI) urinary incontinence. Linear and log binomial regressions were used to calculate mean differences and risk ratios (RR) with 95% confidence intervals (CI). Restricted cubic splines were generated to explore nonlinear relationships.

RESULTS

Among 27 254 women at a mean age of 44.2 years, any urinary incontinence was reported by 32.1%, SUI by 20.9%, UUI by 2.4%, and MUI by 8.6%. For all outcomes, increases in risk were similar with higher BMI and waist circumference. The estimates of association were strongest for MUI (RR 1.10, 95% CI 1.08;1.12 and RR 1.12, 95% CI 1.10;1.14 for half a standard deviation increase in BMI and waist circumference, respectively). While increases in risk of the other outcomes were seen across the entire range of BMI and waist circumference, the risk of SUI rose until BMI 28 kg/m² (waist circumference 95 cm), and then fell slightly.

CONCLUSIONS

Symptoms of urinary incontinence and prevalence of any urinary incontinence, SUI, UUI, and MUI increased with higher BMI and waist circumference. Self-reported BMI and waist circumference were equally predictive of urinary incontinence.

Differences in Occurrence, Risk Factors and Severity of Early-onset Atopic Dermatitis among Preterm and Term Children

This prospective birth cohort followed 150 preterm and 300 term newborns during the first year of life to assess possible differences in risk factors, age at onset, anatomical location, and severity of atopic dermatitis. Atopic dermatitis was diagnosed clinically, and severity was assessed using Eczema Area Severity Index (EASI). DNA was analysed for filaggrin gene mutations. Parents were asked about environmental exposures and emollient use. Atopic dermatitis during the first year of life was observed in 21.2% of children and was more common in term children compared with preterm children (26.7% vs 11.7%, p < 0.001), with lower age of onset (4 vs 6 months, p < 0.05) and more severe disease at onset (EASI: 4.8 vs 0.4, p < 0.0005). Environmental risk factors for atopic dermatitis were essentially similar for preterm and term born children, apart from winter and autumn births. Filaggrin gene mutations were less common in preterm than term children (4.1% vs 9.2%, p = 0.06).

Sexual health in parous women with a history of polycystic ovary syndrome: A national cross-sectional study in Denmark

OBJECTIVE

To examine associations between polycystic ovary syndrome (PCOS) and sexual health in midlife.

METHODS

We included 31 645 mothers from the Danish National Birth Cohort who participated in a Maternal Follow up in 2013-14. A lifetime PCOS diagnosis was self-reported. Sexual health was assessed by specific sexual problems including reduced sexual desire, insufficient lubrication, difficulty in obtaining orgasm, vaginismus and pain during intercourse within the past year. We also generated a combined outcome which was positive if the women reported one or more sexual problems. Logistic regression was used to estimate adjusted odds ratios (aOR) for sexual problems with 95% confidence intervals (CI).

RESULTS

Participants were on average 44 years old, and 920 women (2.9%) had ever had PCOS. One or more sexual problems were more often reported in women with PCOS compared with other women (42.6% versus 36.3%, aOR 1.29, 95% CI 1.13-1.48). Especially reduced sexual desire (25.6% versus 21.0%, aOR 1.29, 95% CI 1.10-1.50) and dyspareunia (11.4% versus 8.7%, aOR 1.34, 95% CI 1.09-1.66) were more frequent in women with PCOS. These associations were slightly weakened when further adjusting for mental and somatic health problems.

CONCLUSION

Our data suggest that PCOS is linked to long-term impaired sexual health, especially reduced sexual desire and dyspareunia.

Psychological well-being and worries among pregnant women in the first trimester during the early phase of the COVID-19 pandemic in Denmark compared with a historical group: A hospital-based cross-sectional study

INTRODUCTION

A pandemic may negatively influence psychological well-being in the individual. We aimed to assess the potential influence of the first national lockdown in Denmark (March to June 2020) due to the COVID-19 pandemic on psychological well-being and the content and degree of worries among pregnant women in early pregnancy.

MATERIAL AND METHODS

In this hospital-based cross-sectional study based on self-reported data we compared psychological well-being and worries among women who were pregnant during the first phase of the pandemic (COVID-19 group) (n = 685), with women who were pregnant the year before (Historical group) (n = 787). Psychological well-being was measured by the five-item World Health Organization Well-being Index (WHO-5), using a score ≤50 as indicator of reduced psychological well-being. Differences in WHO-5 mean scores and in the prevalence of women with score ≤50 were assessed using general linear and log-binomial regression analyses. The Cambridge Worry Scale was used to measure the content and degree of major worries. To detect differences between groups, Pearson's Chi-square test was used.

RESULTS

We found no differences in mean WHO-5 score between groups (mean difference) 0.1 (95% CI -1.5 to 1.6) or in the prevalence of women with WHO-5 score ≤50 (prevalence ratio 1.04, 95% CI 0.83-1.29) in adjusted analyses. A larger proportion of women in the COVID-19 group reported major worries about Relationship with husband/partner compared with the Historical group (3% [n = 19] vs 1% [n = 6], p = 0.04), and 9.2% in the COVID-19 group worried about the possible negative influence of the COVID-19 restrictions.

CONCLUSIONS

Our findings indicate that national restrictions due to the COVID-19 pandemic did not influence the psychological well-being or the content and degree of major worries among pregnant women. However, a larger proportion of women in the COVID-19 group reported major worries concerning Relationship with husband/partner compared with the Historical group and 9.2% in the COVID-19 group worried about the possible negative influence of the COVID-19 restrictions.

Prenatal antibiotic exposure and birth weight

BACKGROUND/OBJECTIVES

Current research suggests an association between antibiotic use in early life and later obesity. Less is known about prenatal antibiotic exposure and foetal growth. We investigated the association between prenatal antibiotic exposure and birth weight.

METHODS

Data from the Danish National Birth Cohort were linked to the Danish National Medical Birth Registry. Exposure was self-reported antibiotic use in pregnancy. Outcome was registered birth weight. Multivariable linear regression models were adjusted for confounders defined a priori.

RESULTS

A total of 63 300 mother-child dyads from 1996 to 2002 were included. Overall, prenatal antibiotic exposure was not associated with birth weight (-8.90 g, 95%CI: -19.5- +1.64 g, p = 0.10). Findings were similar for those born term and preterm. Antibiotic exposure in second to third trimester, compared to no exposure, was associated with lower birth weight (-12.6 g, 95%CI: -24.1 to -1.1 g, p = 0.03). In sex-stratified analyses, there were no observed associations between antibiotics and birth weight. With further stratifications, prenatal antibiotic exposure and birth weight were associated in boys who were preterm (+91.0 g, 95%CI: +6.8 g- +175.2 g, p = 0.03) but not among girls who were preterm (-44.0 g, 95%CI: -128.1 to +40.0 g, p = 0.30).

CONCLUSIONS

Prenatal antibiotic exposure is not consistently associated with birth weight.

Maternal characteristics and pregnancy outcomes in the NICE birth cohort: an assessment of self-selection bias

BACKGROUND

Prospective birth cohorts are essential for identifying associations between exposures and outcomes. However, voluntary participation introduces a potential bias due to self selection since the persons that chose to participate may differ in background characteristics and behaviors.

OBJECTIVES

To investigate potential bias due to self-selection in the Nutritional impact on Immunological maturation during Childhood in relation to the Environment (NICE) birth cohort in northern Sweden.

METHODS

Women in the NICE birth cohort (N = 621) were compared to nonparticipating pregnant women in Norrbotten County in northern Sweden who were eligible for participation (N = 4976) regarding maternal characteristics and lifestyle. Maternal characteristics and pregnancy outcomes were compared between the groups and associations between exposures (smoking, folic acid, BMI, parity, education) and pregnancy outcomes (birth weight and gestational age) were analyzed by linear regression analyses, examining any interaction with the group.

RESULTS

NICE participants were more highly educated, older and more likely to cohabit than the non-participants. They more often took folic acid and multivitamin supplements and less often smoked during early pregnancy. Pregnancy outcomes (mode of delivery, gestational age at delivery, birth weight and APGAR score) did, however, not differ significantly between participants and non-participants. Smoking, BMI, education and parity affected gestational age and birth weight, but the associations were of similar magnitude in participants and non-participants, with no significant effect on the group.

CONCLUSION

Self-selection to the NICE study was evident in some factors related to lifestyle and socioeconomic characteristics but did not appear to skew pregnancy outcomes or alter well-known effects of certain lifestyle parameters on pregnancy outcomes.

Menstrual pain and sexual health in mothers-A cross-sectional study in the Danish National Birth Cohort

INTRODUCTION

Prevalence and consequences of menstrual pain have mainly been studied in younger women. We aimed to describe the prevalence of menstrual pain in mothers and its association with sexual problems.

MATERIAL AND METHODS

A cross-sectional study using questionnaire data from the Maternal Follow Up (2013-2014) in the Danish National Birth Cohort (1996-2002). Of 82 569 eligible mothers, 43 639 (53%) completed the follow up. Of these, 24 000 women had a partner, and answered the questions on menstrual pain. Log binomial regression was used to calculate prevalence proportion ratios (PPR) with 95% CI for the association between menstrual pain and specific sexual problems.

RESULTS

Menstrual pain was reported by 16 464 women (69%), and severe menstrual pain by 19%. Treatment had previously been requested by 19% of women with menstrual pain. The most common treatment was oral contraceptives, but for 18% of women seeking treatment, no treatment was given. Women with menstrual pain were more likely to report reduced sexual desire (PPR 1.22, 95% CI 1.15-1.29), vaginismus (PPR 1.31, 95% CI 0.96-1.78), and dyspareunia (PPR 1.63, 95% CI 1.47-1.81), in particular deep dyspareunia (PPR 1.92, 95% CI 1.67-2.20).

CONCLUSIONS

A majority of Danish mothers in mid-life experienced menstrual pain, and these women more often reported reduced sexual desire, vaginismus, and deep dyspareunia. Few women sought and received treatment for menstrual pain. Healthcare practitioners should be aware that menstrual pain can affect parous women and co-occurs with sexual problems. Future studies should identify barriers to seeking and receiving adequate treatment for menstrual pain.

Lifestyle Habits among Pregnant Women in Denmark during the First COVID-19 Lockdown Compared with a Historical Period-A Hospital-Based Cross-Sectional Study

The first national lockdown in Denmark due to the COVID-19 pandemic was declared on 11 March 2020. From this date, national restrictions were imposed. We aimed to assess the potential influence of this first nationwide lockdown on exercise, alcohol consumption, and smoking in early pregnancy. Using a cross-sectional study based on routinely collected patient-reported data, we compared the lifestyle habits of women who were pregnant during the first phase of the pandemic (COVID-19 group) (n = 685) with those of women who were pregnant the year before (Historical group) (n = 787). We found a reduction in any exercise (PR = 0.91, 95% CI (0.84 to 0.99), in adherence to national recommendations of exercise (PR = 0.89, 95% CI (0.80 to 0.99), in cycling (15% vs. 28%, p < 0.0001), and swimming (0.3% vs. 3%, p = 0.0002) in the COVID-19 group compared with the Historical group. The prevalence of binge drinking was reduced in the COVID-19 group compared with the Historical group (PR = 0.80, 95% CI (0.68 to 0.93). In contrast, the prevalence of any weekly alcohol consumption and smoking cessation during pregnancy was similar between groups. Our findings indicate that national restrictions due to the COVID-19 pandemic influenced the lifestyle habits of pregnant women and should be addressed in antenatal counseling.

Maternal weight change from prepregnancy to 18 months postpartum and subsequent risk of hypertension and cardiovascular disease in Danish women: A cohort study

BACKGROUND

One-fourth of women experience substantially higher weight years after childbirth. We examined weight change from prepregnancy to 18 months postpartum according to subsequent maternal risk of hypertension and cardiovascular disease (CVD).

METHODS AND FINDINGS

We conducted a cohort study of 47,966 women with a live-born singleton within the Danish National Birth Cohort (DNBC; 1997-2002). Interviews during pregnancy and 6 and 18 months postpartum provided information on height, gestational weight gain (GWG), postpartum weights, and maternal characteristics. Information on pregnancy complications, incident hypertension, and CVD was obtained from the National Patient Register. Using Cox regression, we estimated adjusted hazard ratios (HRs; 95% confidence interval [CI]) for hypertension and CVD through 16 years of follow-up. During this period, 2,011 women were diagnosed at the hospital with hypertension and 1,321 with CVD. The women were on average 32.3 years old (range 18.0-49.2) at start of follow-up, 73% had a prepregnancy BMI <25, and 27% a prepregnancy BMI ≥25. Compared with a stable weight (±1 BMI unit), weight gains from prepregnancy to 18 months postpartum of >1-2 and >2 BMI units were associated with 25% (10%-42%), P = 0.001 and 31% (14%-52%), P < 0.001 higher risks of hypertension, respectively. These risks were similar whether weight gain presented postpartum weight retention or a new gain from 6 months to 18 months postpartum and whether GWG was below, within, or above the recommendations. For CVD, findings differed according to prepregnancy BMI. In women with normal-/underweight, weight gain >2 BMI units and weight loss >1 BMI unit were associated with 48% (17%-87%), P = 0.001 and 28% (6%-55%), P = 0.01 higher risks of CVD, respectively. Further, weight loss >1 BMI unit combined with a GWG below recommended was associated with a 70% (24%-135%), P = 0.001 higher risk of CVD. No such increased risks were observed among women with overweight/obesity (interaction by prepregnancy BMI, P = 0.01, 0.03, and 0.03, respectively). The limitations of this observational study include potential confounding by prepregnancy metabolic health and self-reported maternal weights, which may lead to some misclassification.

CONCLUSIONS

Postpartum weight retention/new gain in all mothers and postpartum weight loss in mothers with normal-/underweight may be associated with later adverse cardiovascular health.

Risk of selection bias due to non-participation in a cohort study on pubertal timing

BACKGROUND

Non-participation in aetiologic studies of pubertal timing is frequent. However, little effort has been given to explore the risk and potential impact of selection bias in studies of pubertal timing.

OBJECTIVE

We aimed to explore the risk of selection bias due to non-participation in a newly established puberty cohort.

METHODS

We evaluated whether three maternal exposures chosen a priori (pre-pregnancy obesity, smoking, and alcohol drinking during pregnancy) were associated with participation, whether pubertal timing was associated with participation, and whether selection bias influenced the associations between these exposures and pubertal timing. In total, 22 439 children from the Danish National Birth Cohort born 2000-2003 were invited to the Puberty Cohort and 15 819 (70%) participated. Exposures were self-reported during pregnancy. Pubertal timing was measured using a previously validated marker, "the height difference in standard deviations" (HD:SDS), which is the difference between pubertal height and adult height, both in standard deviations. For this study, pubertal height at around 13 years in sons and around 11 years in daughters was obtained from an external database, and adult height was predicted based on parental height reported by mothers.

RESULTS

Participation was associated with most exposures but not with pubertal timing, measured by HD:SDS. The associations between exposures and HD:SDS were comparable for participants only and all invited for participation.

CONCLUSION

In conclusion, the risk of selection bias in aetiologic studies on pubertal timing in the Puberty Cohort appears minimal.

Sexual Health in Women with Inflammatory Bowel Disease in the Danish National Birth Cohort

BACKGROUND AND AIMS

Previous studies indicate an increased risk of sexual dysfunction in women with inflammatory bowel disease [IBD] but none have examined sexual function in a large population-based cohort.

METHODS

To investigate the risk of sexual dysfunction in women with IBD, we used data from the Danish National Birth Cohort, a nationwide study of 92 274 pregnant women recruited during 1996-2002. We performed a cross-sectional study based on mothers who participated in the Maternal Follow-up in 2013-14. The outcome was self-reported sexual health. Information regarding demographics and IBD characteristics was retrieved from the Danish National Patient Register. Using regression models and adjusting for important confounders, we compared sexual function in women with and without IBD.

RESULTS

The study population consisted of 38 011 women including 196 [0.5%] with Crohn's disease [CD] and 409 [1.1%] with ulcerative colitis [UC]. Median age was 44 years. Compared to women without IBD, women with UC did not have significantly decreased sexual function, while women with CD had more difficulty achieving orgasm (adjusted odds ratio [aOR] 1.53; 95% confidence interval [CI] 1.02-2.30], increased dyspareunia [aOR 1.71; 95% CI 1.11-2.63] and deep dyspareunia [aOR 2.00; 95% CI 1.24-3.22]. The risk for difficulty achieving orgasm and deep dyspareunia was further increased within 2 years of an IBD-related contact/visit [aOR 1.81; 95% CI 1.11-2.95; and aOR 2.37; 95% CI 1.34-4.19].

CONCLUSIONS

Women with CD have significantly increased difficulty achieving orgasm and increased dyspareunia. Physicians should be cognizant of and screen for sexual dysfunction in this group of patients.

The PRIDE Study: Evaluation of online methods of data collection

BACKGROUND

Large birth cohort studies are extremely valuable in assessing associations between early life exposures and long-term outcomes. Establishing new birth cohorts is challenging due to declining participation rates. Online methods of data collection may increase feasibility, but have not been evaluated thoroughly.

OBJECTIVE

The primary objective of the ongoing PRegnancy and Infant DEvelopment (PRIDE) Study is to identify exposures during pregnancy and in early life that may affect short-term or long-term health of mother and/or child. In this manuscript, we aimed to evaluate methods of recruitment and online data collection applied.

POPULATION

Dutch women aged ≥18 years in early pregnancy.

DESIGN

Prospective cohort study.

METHODS

Initially, only prenatal care providers recruited participants, but alternative recruitment methods were added as a result of disappointing participation rates, including collaboration with "Moeders voor Moeders" (organisation that visits women in early pregnancy) and Facebook advertisements. Data on demographic characteristics, obstetric history, maternal health, life style factors, occupational exposures, nutrition, pregnancy complications, and infant outcomes are primarily collected through Web-based questionnaires at multiple time points during and after pregnancy. Additional data collection components include paternal questionnaires, blood and saliva sampling, and linkage to medical records.

PRELIMINARY RESULTS

By September 2019, 9573 women were included in the PRIDE Study, of which 1.3% completed paper-based questionnaires. Mean age of the women analysed was 30.6 years, 71.1% had a high level of education, 57.2% were primiparae, and mean gestational age at enrolment was 9.9 (range 3, 37) weeks, with slight differences between recruitment methods. Pregnancy outcome was known for 89.8%. Retention rate at 6 months after the estimated date of delivery was estimated at 70%. Multiple validation studies conducted within the PRIDE Study indicated high data quality.

CONCLUSION(S)

Although challenging and time-consuming, online methods for recruitment and data collection may enable the establishment of new birth cohort studies.

Use of Personal Care Products and Semen Quality: A Cross-Sectional Study in Young Danish Men

Personal care products (PCPs) may contain multiple chemicals capable of harming male reproductive function. The aim of this study was, therefore, to assess aggregated PCP exposure and potential associations with measures of semen quality in young men. Participants (n = 1058, age 18–21) were sampled among young men from the Danish National Birth Cohort (DNBC). Upon recruitment in 2017–2019, each man answered an online questionnaire and provided a semen sample. Exposure to 12 common types of PCPs was derived from the questionnaire, and the extent of use and co-use was analyzed. We applied a negative binomial regression model to estimate percentage differences in semen parameters between low, medium and high PCP exposure groups. All participants were exposed to at least one PCP more than once a week, resulting in a mean number (SD) of 5.3 (2.0) PCPs currently used. Most participants (92%) were also exposed to fragranced products on a weekly basis. Little association was observed between aggregated exposure to PCPs and sperm concentration, total sperm count, semen volume, sperm motility and morphology. Despite prevalent use of multiple PCPs, we found little indication of adverse effects of aggregated overall or fragranced PCP exposure on semen quality.

Mode of birth and long-term sexual health: a follow-up study of mothers in the Danish National Birth Cohort

OBJECTIVES

To investigate the relation between mode of birth and women's long-term sexual health.

DESIGN

Maternal follow-up of the Danish National Birth Cohort (1996-2002) in 2013-2014 including questions on sexual health. Logistic regression was used to relate registry-based information about mode of birth and perineal tears with data on sexual problems.

SETTING

Denmark.

PARTICIPANTS

Of 82 569 eligible mothers in the Danish National Birth Cohort, 43 639 (53%) completed the follow-up. Of these, 37 417 women had a partner, and answered at least one question on sexual health.

MAIN OUTCOME MEASURES

Self-reported sexual health.

RESULTS

Participants were on average 44 years old, and 16 years after their first birth. The frequency of sexual problems among women with only spontaneous vaginal births, the reference group, was 37%. For women who only had caesarean sections, more problems were reported (OR 1.18; 95% CI 1.09 to 1.28). For women who had a spontaneous vaginal birth subsequent to a caesarean, and for women with only vaginal births who had experienced one or more instrumental vaginal births, the odds of sexual problems did not differ from women with only spontaneous vaginal births (OR 1.00; 95% CI 0.91 to 1.11) and (OR 1.01; 95% CI 0.95 to 1.08), respectively.

CONCLUSIONS

These findings indicate that caesarean section does not protect against long-term sexual problems. Rather, vaginal birth, even after caesarean section, was associated with fewer long-term sexual problems.

Limited evidence of non-response bias despite modest response rate in a nationwide survey of long-term cancer survivors-results from the NOR-CAYACS study

PURPOSE

Declining response rates threaten the generalizability of health surveys. We investigate (1) the effect of item order on response rate; (2) characteristics of early , late and non-responders; and (3) potential non-response bias in a population-based health survey of childhood, adolescent and young adult cancer survivors (CAYACS).

METHODS

We mailed a questionnaire survey to 5361 eligible CAYACS identified by the Cancer Registry of Norway (CRN), representing a range of cancer diagnoses. The 302-item questionnaire included a range of survivorship-related questions and validated patient-reported outcome measures. To investigate item-order effects on response rates, we constructed two versions of the questionnaire presenting cancer-related or socio-demographic items first. The CRN provided demographic and clinical information for the total population. Risk of non-response bias was estimated by (1) comparing outcomes between early and late responders (answered after a reminder), and (2) by applying inverse probability of participation weights to construct a total population (with 100% response) and then compare 21 a priori selected outcomes between early responders, all responders (early + late) and the total population (all eligible).

RESULTS

Survey item order did not affect response rates (cancer first 49.8% vs socio-demographic first 50.2%). Shorter time since diagnosis, male gender and a malignant melanoma diagnosis remained significant predictors of non-response in a multivariable multinomial regression model. There were no significant differences on 16/21 survey outcomes between early and late responders, and 18/21 survey outcomes between early responders, all responders and the total population.

CONCLUSION

Despite a modest response rate, we found little evidence for a response bias in our study.

IMPLICATIONS FOR CANCER SURVIVORS

Surveys of survivor-reported outcomes with low response rates may still be valuable and generalizable to the total survivor population.

Maternal blood pressure and hypertensive disorders during pregnancy and childhood respiratory morbidity: the Generation R Study

Pre-eclampsia is associated with an increased risk of bronchopulmonary dysplasia, wheezing and asthma in later childhood. Currently, there are no studies available investigating maternal blood pressure measurements during multiple time-points in pregnancy and respiratory outcome measures in the child.We examined the associations of maternal blood pressure and hypertensive disorders with the risk of lower lung function, wheezing and asthma in children aged 10 years. This study among 4894 children was embedded in a population-based prospective cohort study. We used multivariate analyses, taking lifestyle and socioeconomic factors into account.We observed consistent associations per 5 mmHg higher maternal blood pressure in early pregnancy with a lower forced expiratory volume in 1 s/forced vital capacity ratio (z-score -0.03 (95% CI -0.05- -0.01)) and per 5 mmHg higher blood pressure in late pregnancy with a higher risk for current wheezing and current asthma (OR 1.07 (95% CI 1.02-1.12) and 1.06 (95% CI 1.00-1.11), respectively). We found no associations of maternal hypertensive disorders during pregnancy with child lung function, current wheezing or current asthma.Our results suggest that higher blood pressure in pregnant women is associated with lower lung function and increased risks of current wheezing and current asthma in children. The associations may be trimester specific.