Short interpregnancy intervals and adverse perinatal outcomes in high-resource settings: An updated systematic review

Trends in Short Interpregnancy Interval Births in the United States, 2016-2022

OBJECTIVE

To measure contemporary trends in the prevalence of short interpregnancy interval (IPI) births in the United States.

METHODS

We conducted a repeated cross-sectional analysis using 2016-2022 natality data from the National Vital Statistics System. We included all singleton live births to individuals with at least one prior live birth. We examined trends over time in short IPIs less than 18 months, as well as for specific durations within this time frame (less than 6 months, 6-11 months, and 12-17 months), using linear probability models that estimated changes in the prevalence of each IPI duration over time. We then estimated the prevalence of each short IPI duration by maternal race and ethnicity, socioeconomic characteristics (age, education, insurance payer at delivery), and geography (U.S. census region, state of residence).

RESULTS

The study sample included 14,770,411 singleton live births to individuals with at least one prior live birth in 2016-2022. Roughly a third (29.8%) of births had an overall IPI of less than 18 months (5.0% less than 6 months, 11.0% 6-11 months, and 13.8% 12-17 months). For IPIs less than 6 months, a slight statistical decline in prevalence was identified over the study period in unadjusted and adjusted models (adjusted annual percentage point change -0.02, 95% CI, -0.03 to -0.02). Slight statistical increases in the prevalence of IPIs of 6-11 and 12-17 months were identified in unadjusted models but were no longer significant and reversed direction in adjusted models, respectively. Long-standing inequities in the distribution of the shortest IPIs (less than 6 months) were stable compared with prior work across the indicators examined in this study.

CONCLUSION

Overall, it appears the prevalence of short IPIs has remained stable between 2016 and 2022.

Interpregnancy interval after vacuum delivery and subsequent perinatal outcomes

OBJECTIVE

To evaluate whether a short interpregnancy interval (IPI) after vacuum extraction (VE), poses similar perinatal risks in a subsequent pregnancy.

METHODS

This was a retrospective, single-center cohort study between 2011 and 2021. Nulliparous women with term, singleton VE deliveries and with known pregnancy outcomes in their subsequent pregnancy were eligible for inclusion in the study. Each woman was allocated into one of two groups based on the IPI, <18 months and between 18 and 60 months. The primary outcome was the risk of spontaneous preterm birth (PTB) <37 weeks in the consecutive birth.

RESULTS

We included 1094 pregnancies: 212 (19.4%) with IPI <18 months and 882 (80.6%) with IPI between 18 and 60 months following the previous VE delivery. The VE characteristics were comparable between the groups. Young maternal age was a risk factor for a short IPI (28.0 ± 4.8 vs 30.3 ± 4 years, P < 0.01). Spontaneous PTB <37 weeks was significantly higher in the IPI <18 months group with 18-60 months (7.1% vs 2.6%, P = 0.002). Polynomial regression analysis also confirmed a significantly increased risk of preterm birth <37 weeks (P < 0.01). Short IPI <18 months was also associated with an increase in the risk of low birthweight <2500 g (6.1% vs 2.8%, P = 0.02) and admission to the neonatal intensive care unit (6.1% vs 2.6%, P = 0.013). The incidence of recurrent VE, albeit significant (2.3% vs 4.9%, P = 0.049), was low in both groups. No differences were noted in any of the other secondary outcomes.

CONCLUSION

Short IPI (<18 months) following term VE delivery is associated with higher neonatal risks, particularly PTB, in the subsequent pregnancy. These findings are particularly important when counseling women planning an optimal IPI.

Interpregnancy intervals and behavioural outcomes in children: A population-based longitudinal study

BACKGROUND

While the physical health consequence of short interpregnancy intervals (IPIs) is well documented, its mental health impact is not well explored. This study aimed to examine the associations between IPIs and behavioural outcomes in children born following the interval at four developmental time points between ages 7 and 16.

METHODS

Our study sample comprised participants in the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort, an ongoing population-based longitudinal birth cohort in Bristol, Avon, United Kingdom. Behavioural problems, including total behavioural difficulties, hyperactivity, emotional symptoms, conduct problems, peer-problems, and problems of pro-social behaviour, were assessed using the Strengths and Difficulties Questionnaire (SDQ). Over 2300 mothers and their singleton children were included in this study. Generalized Estimating Equations (GEE) were used to estimate odds ratios for the associations.

RESULTS

Children born to mothers with short IPI (<6 months) were 1.54 (95%CI: 1.12-2.11), 1.42 (95% CI: 1.12-1.81) and 1.37 (95%CI: 1.04-1.79) times more likely to have total behavioural difficulties, conduct problems and hyperactivity/inattention problems across the child's age, respectively, compared with children of mothers with IPIs of 18-23 months. We found no evidence of associations between short IPI (<6 months) and emotional symptoms, peer-relationship problems and pro-social behaviour problems.

CONCLUSION

Short IPI (<6 months) was associated with externalising (conduct and hyperactivity/inattention) but not internalising (emotional and peer-relationship problems) problems. Further studies are needed to confirm this association and elucidate the underlying mechanisms.

Demographic and pregnancy-related predictors of postnatal contraception uptake: A cross-sectional study

OBJECTIVE

To examine the uptake of postnatal contraception (PNC) and experiences of PNC care across a geographical region of England.

DESIGN

Cross-sectional online survey.

SETTING

The North East and North Cumbria Integrated Care System (ICS).

POPULATION

Women who had completed a pregnancy in the previous 3 years.

METHODS

The uptake of PNC by accessed method(s) and the availability of preferred method(s) is described, and adjusted odds ratios are reported for group differences in uptake by characteristics of interest.

MAIN OUTCOME MEASURES

Uptake of medically prescribed/administered contraception and uptake of long-acting reversible contraception (LARC) during the postnatal period, and access to preferred PNC methods.

RESULTS

Although almost half of respondents (47.1%; n = 1178) reinitiated some form of sexual activity during the postnatal period, only 38.7% (n = 969) of respondents accessed a medically prescribed/administered contraceptive method postnatally, and only 15.5% (n = 389) of respondents accessed a LARC. It is a matter of concern that 18.8% (n = 451) of respondents indicated that they were unable to access their preferred PNC. In multivariate analysis, younger age, lower household income, higher multiparity, operative delivery, unplanned pregnancy and not breastfeeding were significant predictors of higher PNC uptake.

CONCLUSIONS

The uptake of PNC in this cohort was low, with almost a fifth of women unable to access their preferred method. However, there was some evidence that women belonging to groups perceived to be at risk of rapid repeat pregnancy were more likely to access reliable PNC methods.

Interpregnancy interval and adverse perinatal outcomes: A within-individual comparative method

Background and Aim

Previously observed associations between interpregnancy interval (IPI) and perinatal outcomes using a between-individual method may be confounded by unmeasured maternal factors. This study aims to examine the association between IPI and adverse perinatal outcomes using within-individual comparative analyses.

Methods

We studied 10,647 individuals from the National Institute of Child Health and Human Development Consecutive Pregnancies Study in Utah with ≥3 liveborn singleton pregnancies. We matched two IPIs per individual and used conditional logistic regression to examine the association between IPI and adverse perinatal outcomes, including preterm birth (PTB, <37 weeks' gestation), small-for-gestational-age (SGA, <10th percentile of sex-specific birthweight for gestational age), low birthweight (LBW, <2,500 g), and neonatal intensive care unit (NICU) admission. Point and 95% confidence interval (CI) estimates were adjusted for factors that vary across pregnancies within individuals.

Results

CIs did not unequivocally support either an increase or a decrease in the odds of PTB (adjusted odds ratio [aOR]: 1.31, 95% CI: 0.87, 1.96), SGA (aOR: 0.81, 95% CI: 0.51, 1.28), LBW (aOR: 1.59, 95% CI: 0.90, 2.80), or NICU admission (aOR: 0.96, 95% CI: 0.66, 1.40) for an IPI <6 months compared to 18-23-months IPI (reference), and neither did the CIs for the aOR of IPIs of 6-11 and 12-18 months compared to the reference. In contrast, an IPI ≥24 months was associated with increased odds of LBW (aOR: 1.66, 95% CI: 1.03, 2.66 for 24-29 months; aOR: 2.27, 95% CI: 1.21, 4.29 for 30-35 months; and aOR: 2.09, 95% CI: 1.17, 3.72 for ≥36 months).

Conclusions

Using a within-individual comparative method, we did not find evidence that a short IPI compared to the recommended IPI of 18-23 months was associated with increased odds of PTB, SGA, LBW, and NICU admission. IPI ≥ 24 months was associated with increased odds of delivering an LBW infant.

Short inter-pregnancy interval and birthweight: a reappraisal based on a follow-up study of all women in Norway with two singleton deliveries during 1970-2019

We studied mean changes in birthweight from the first to the second delivery according to length of the inter-pregnancy interval. We also studied recurrence risk of low birthweight, preterm birth and perinatal death. We followed all women in Norway from their first to their second singleton delivery at gestational week 22 or beyond during the years 1970-2019, a total of 654 100 women. Data were obtained from the Medical Birth Registry of Norway. Mean birthweight increased from the first to the second delivery, and the increase was highest in pregnancies conceived < 6 months after the first delivery; adjusted mean birthweight increase 227 g (g) (95% CI; 219-236 g), 90 g higher than in pregnancies conceived 6-11 months after the first delivery (137 g (95% CI; 130-144 g)). After exclusion of women with a first stillbirth, the mean increase in birthweight at inter-pregnancy interval < 6 months was attenuated (152 g, 95% CI; 143-160 g), but remained higher than at longer inter-pregnancy intervals. This finding was particularly prominent in women > 35 years (218 g, 95% CI; 139 -298 g). In women with a first live born infant weighing < 2500 g, mean birthweight increased by around 1000 g to the second delivery, and the increase was most prominent at < 6 months inter-pregnancy interval. We found increased recurrence risk of preterm birth at inter-pregnancy interval < 6 months, but no increased recurrence risk of low birthweight, small for gestational age infant or perinatal death. In conclusion, we found the highest mean increase in birthweight when the inter-pregnancy interval was short. Our results do not generally discourage short pregnancy intervals.

Does reversible postpartum contraception reduce the risk of pregnancy condition recurrence? A longitudinal claims-based study from Maine

PURPOSE

To estimate the effect of reversible postpartum contraception use on the risk of recurrent pregnancy condition in the subsequent pregnancy and if this effect was mediated through lengthening the interpregnancy interval (IPI).

METHODS

We used data from the Maine Health Data Organization's Maine All Payer Claims dataset. Our study population was Maine women with a livebirth index pregnancy between 2007 and 2019 that was followed by a subsequent pregnancy starting within 60 months of index pregnancy delivery. We examined recurrence of three pregnancy conditions, separately, in groups that were not mutually exclusive: prenatal depression, hypertensive disorders of pregnancy (HDP), and gestational diabetes (GDM). Effective reversible postpartum contraception use was defined as any intrauterine device, implant, or moderately effective method (pills, patch, ring, injectable) initiated within 60 days of delivery. Short IPI was defined as ≤ 12 months. We used log-binomial regression models to estimate risk ratios and 95 % confidence intervals, adjusting for potential confounders.

RESULTS

Approximately 41 % (11,448/28,056) of women initiated reversible contraception within 60 days of delivery, the prevalence of short IPI was 26 %, and the risk of pregnancy condition recurrence ranged from 38 % for HDP to 55 % for prenatal depression. Reversible contraception initiation within 60 days of delivery was not associated with recurrence of the pregnancy condition in the subsequent pregnancy (aRR ranged from 0.97 to 1.00); however, it was associated with lower risk of short IPI (aRR ranged from 0.67 to 0.74).

CONCLUSION(S)

Although initiation of postpartum reversible contraception within 60 days of delivery lengthens the IPI, our findings suggest that it does not reduce the risk of prenatal depression, HDP, or GDM recurrence. This indicates a missed opportunity for providing evidence-based healthcare and health interventions in the intrapartum period to reduce the risk of recurrence.

Effects of short inter-pregnancy/birth interval on adverse perinatal outcomes in Asia-Pacific region: A systematic review and meta-analysis

BACKGROUND

Short inter-pregnancy or birth interval is associated with an increased risk of adverse perinatal outcomes. However, some emerging evidence questions this association and there are also inconsistencies among the existing findings. This study aimed to systematically review the evidence regarding the effect of short inter-pregnancy or birth intervals on adverse perinatal outcomes in the Asia-Pacific region.

METHODS

A comprehensive search of five databases was conducted targeting studies published between 2000 to 2023. Studies that reported on short inter-pregnancy or birth interval and examined adverse perinatal outcomes, such as low birthweight (LBW) preterm birth (PTB), small for gestational age (SGA), and neonatal mortality were included and appraised for methodological quality using the Joanna Briggs Institute critical appraisal tools. Three reviewers independently screened the studies and performed data extraction. Narrative synthesis and meta-analyses were conducted to summarise the key findings.

RESULTS

A total of 41 studies that fulfilled the inclusion criteria were included. A short-interpregnancy interval was associated with an increased risk of low birthweight (odds ratio [OR] = 1.65; 95%CI:1.39, 1.95), preterm birth (OR = 1.50; 95%CI: 1.35, 1.66), and small for gestational age (OR = 1.24; 95%CI:1.09, 1.41). We also found elevated odds of early neonatal mortality (OR = 1.91; 95%CI: 1.11, 3.29) and neonatal mortality (OR = 1.78; 95%CI: 1.25, 2.55) among women with short birth intervals.

CONCLUSION

This review indicates that both short inter-pregnancy and birth interval increased the risk of adverse perinatal outcomes. This underscores the importance of advocating for and implementing strategies to promote optimal pregnancy and birth spacing to reduce the occurrence of adverse perinatal outcomes. Reproductive health policies and programs need to be further strengthened and promote access to comprehensive family planning services and increase awareness about the importance of optimal pregnancy and birth spacing.

Effectiveness of nurse-home visiting in improving child and maternal outcomes prenatally to age two years: a randomised controlled trial (British Columbia Healthy Connections Project)

BACKGROUND

We investigated the effectiveness of Nurse-Family Partnership (NFP), a prenatal-to-age-two-years home-visiting programme, in British Columbia (BC), Canada.

METHODS

For this randomised controlled trial, we recruited participants from 26 public health settings who were: <25 years, nulliparous, <28 weeks gestation and experiencing socioeconomic disadvantage. We randomly allocated participants (one-to-one; computer-generated) to intervention (NFP plus existing services) or comparison (existing services) groups. Prespecified outcomes were prenatal substance exposure (reported previously); child injuries (primary), language, cognition and mental health (problem behaviour) by age two years; and subsequent pregnancies by 24 months postpartum. Research interviewers were masked. We used intention-to-treat analyses. (ClinicalTrials.gov, NCT01672060.) RESULTS: From 2013 to 2016 we enrolled 739 participants (368 NFP, 371 comparison) who had 737 children. Counts for child injury healthcare encounters [rate per 1,000 person-years or RPY] were similar for NFP (223 [RPY 316.17]) and comparison (223 [RPY 305.43]; rate difference 10.74, 95% CI -46.96, 68.44; rate ratio 1.03, 95% CI 0.78, 1.38). Maternal-reported language scores (mean, M [SD]) were statistically significantly higher for NFP (313.46 [195.96]) than comparison (282.77 [188.15]; mean difference [MD] 31.33, 95% CI 0.96, 61.71). Maternal-reported problem-behaviour scores (M [SD]) were statistically significantly lower for NFP (52.18 [9.19]) than comparison (54.42 [9.02]; MD -2.19, 95% CI -3.62, -0.75). Subsequent pregnancy counts were similar (NFP 115 [RPY 230.69] and comparison 117 [RPY 227.29]; rate difference 3.40, 95% CI -55.54, 62.34; hazard ratio 1.01, 95% CI 0.79, 1.29). We observed no unanticipated adverse events.

CONCLUSIONS

NFP did not reduce child injuries or subsequent maternal pregnancies but did improve maternal-reported child language and mental health (problem behaviour) at age two years. Follow-up of long-term outcomes is warranted given that further benefits may emerge across childhood and adolescence.

Racial and ethnic disparities in short interval pregnancy following delivery in Catholic vs non-Catholic hospitals among California Medicaid enrollees

OBJECTIVES

We examined the impact of Catholic hospital delivery on short interval pregnancy in the California 2010-2014 Medicaid population.

STUDY DESIGN

We used Cox regression to estimate the association between hospital affiliation and short interval pregnancy, adjusting for patient factors.

RESULTS

Catholic hospital delivery had increased the risk of pregnancy within 6 months for Black (hazard ratio [HR] 1.11, 95% CI 1.06, 1.17) and Hispanic (HR 1.07, 95% CI 1.05, 1.09) but not for White women (HR 1.02, 95% CI 0.98, 1.05).

CONCLUSIONS

Among California women with Medicaid, Catholic hospital delivery was associated with short interval pregnancy only among women of color.

Maternal Thyroid Dysfunction During Pregnancy as an Etiologic Factor in Autism Spectrum Disorder: Challenges and Opportunities for Research

Background: Autism spectrum disorder (ASD) is a neurodevelopmental condition with unknown etiology. Both genetic and environmental factors have been associated with ASD. Environmental exposures during the prenatal period may play an important role in ASD development. This narrative review critically examines the evidence for a relationship between maternal thyroid dysfunction during pregnancy and ASD in the child. Summary: Studies that assessed the associations of hypothyroidism, hyperthyroidism, hypothyroxinemia, thyroid hormone concentrations, or autoimmune thyroid disease with ASD outcomes were included. Most research focused on the relationship between hypothyroidism and ASD. Multiple population-based studies found that maternal hypothyroidism was associated with higher likelihood of an ASD diagnosis in offspring. Associations with other forms of maternal thyroid dysfunction were less consistent. Findings may have been affected by misclassification bias, survival bias, or publication bias. Studies using medical records may have misclassified subclinical thyroid dysfunction as euthyroidism. Two studies that assessed children at early ages may have misclassified those with ASD as typically developing. Most studies adjusted for maternal body mass index (BMI) and/or mental illness, but not interpregnancy interval or pesticide exposure, all factors associated with fetal survival and ASD. Most studies reported a combination of null and statistically significant findings, although publication bias is still possible. Conclusions: Overall, evidence supported a positive association between maternal thyroid dysfunction during pregnancy and ASD outcomes in the child, especially for hypothyroidism. Future studies could reduce misclassification bias by using laboratory measures instead of medical records to ascertain thyroid dysfunction and evaluating children for ASD at an age when it can be reliably detected. Survival bias could be further mitigated by adjusting models for more factors associated with fetal survival and ASD. Additional research is needed to comprehensively understand the roles of maternal levothyroxine treatment, iodine deficiency, or exposure to thyroid-disrupting compounds in the relationship between maternal thyroid dysfunction and child ASD outcomes.

Postpartum contraception in Australia: opportunities for increasing access in the primary care setting

In Australia, 20% of pregnancies occur within the first year after birth and most are unintended. Both unintended pregnancies and short interpregnancy intervals (<12-18months) can have adverse effects on maternal, infant, and child health. Access to postpartum contraception reduces the risk of unintended pregnancies and short interpregnancy intervals, and supports women in pregnancy planning and birth spacing. In this forum article, we describe how postpartum contraception is currently provided in Australia and highlight opportunities for improving access in the primary care setting.

Interpregnancy interval and adverse birth outcomes: a population-based cohort study of twins

BACKGROUND

To investigate associations between interpregnancy intervals (IPIs) and adverse birth outcomes in twin pregnancies.

METHODS

This retrospective cohort study of 9,867 twin pregnancies in Western Australia from 1980-2015. Relative Risks (RRs) were estimated for the interval prior to the pregnancy (IPI) as the exposure and after the pregnancy as a negative control exposure for preterm birth (< 37 weeks), early preterm birth (< 34 weeks), small for gestational age (SGA: < 10th percentile of birth weight by sex and gestational age) and low birth weight (LBW: birthweight < 2,500 g).

RESULTS

Relative to IPIs of 18-23 months, IPIs of < 6 months were associated with a higher risk of early preterm birth (aRR 1.41, 95% CI 1.08-1.83) and LBW for at least one twin (aRR 1.16, 95% CI 1.06-1.28). IPIs of 6-11 months were associated with a higher risk of SGA (aRR 1.24, 95% CI 1.01-1.54) and LBW for at least one twin (aRR 1.09, 95% CI 1.01-1.19). IPIs of 60-119 months and ≥ 120 months were associated with an increased risk of preterm birth (RR 1.12, 95% CI 1.03-1.22; and (aRR 1.25, 95% CI 1.10-1.41, respectively), and LBW for at least one twin (aRR 1.17, 95% CI 1.08-1.28; and aRR 1.20, 95% CI 1.05-1.36, respectively). IPIs of ≥ 120 months were also associated with an increased risk of early preterm birth (aRR 1.42, 95% CI 1.01-2.00). After negative control analysis, IPIs ≥ 120 months remained associated with early preterm birth and LBW.

CONCLUSION

Evidence for adverse associations with twin birth outcomes was strongest for long IPIs.

Postpartum contraception: A matter of guidelines

The postpartum period is the perfect time to access family planning services. WHO guidelines contraindicate combined hormonal contraceptives postpartum in breastfeeding patients between 6 weeks and 6 months after delivery (Medical Eligibility Criteria category 3). On the contrary, the Faculty of Sexual and Reproductive Healthcare and the Centers for Disease Control and Prevention guidelines do not contraindicate their use in women who breastfeed from 6 weeks to 6 months postpartum. New combined hormonal contraceptives with natural estrogens have never been studied in this setting. Guidelines agree on the prescription of the progestin-only pill postpartum in non-breastfeeding women (category 1). Differences are found in women who breastfeed. In non-breastfeeding women, an implant is considered safe (category 1) by all guidelines, without any distinction in time. Regarding postpartum breastfeeding women, the guidelines for implants give quite different indications but are still permissive. Intrauterine devices are viable options for postpartum contraception but guidelines give different indications about the timing of insertion. Postplacental intrauterine device placement can reduce the subsequent unintended pregnancy rate, particularly in settings at greatest risk of not having recommended postpartum controls. However, it has yet to be understood whether this approach can really have an advantage in high-income countries. Postpartum contraception is not a 'matter of guidelines': it is the best customization for each woman, as early as possible but at the ideal timing.

Prevalence and correlates of very rapid repeat pregnancy: Pregnancy Risk Assessment Monitoring System, United States, 2009-2020

BACKGROUND

Most rapid repeat pregnancies, defined as those occurring within 18 months of a previous birth, are unintended. These pregnancies are associated with later initiation of prenatal care and are more common among people with lower socio-economic status and among racially and ethnically minoritised populations.

OBJECTIVES

To assess prevalence and correlate pregnancies occurring in the immediate period after a live birth in the United States, using the Pregnancy Risk Assessment Monitoring System (PRAMS).

METHODS

We assessed data from the 2009-2020 PRAMS, a population-based survey of perinatal maternal characteristics of mothers of liveborn infants in US locations. We assessed pregnancies reported during the immediate postpartum period (approximately 2-6 months post-delivery), and term this 'very rapid repeat pregnancy' (VRRP). We assessed the adjusted prevalence of VRRP from 2009 to 2020. From 2016 to 2020, we calculated adjusted prevalence ratios (aPR) with 95% confidence intervals (CI) for maternal characteristics.

RESULTS

The adjusted prevalence of VRRP ranged from 0.38% (95% CI: 0.29, 0.48) in 2009 to 0.76% (95% CI: 0.61, 0.91) in 2020. Demographic characteristics associated with VRRP included younger age, lower educational attainment, and being unmarried. Black mothers had a higher prevalence of VRRP compared to white mothers. Mothers who attended a healthcare visit in the 12 months preconception had a lower prevalence of VRRP as did mothers who attended a postpartum check-up, compared to their counterparts without these visits. Among those receiving prenatal care, mothers whose prenatal healthcare provider asked about postpartum contraception birth had a lower prevalence of VRRP, compared to those not asked about postpartum contraception.

CONCLUSIONS

VRRP appeared to increase over time in 2009-2020. Mothers who are younger, Black, have lower educational attainment, or who did not attend healthcare visits before or after pregnancy had a higher prevalence of VRRP and may comprise a population who would benefit from additional family planning resources.

Short birth interval prevalence, determinants and effects on maternal and child health outcomes in Asia-Pacific region: a systematic review and meta-analysis protocol

BACKGROUND

Short birth interval (SBI) has been linked to an increased risk of adverse maternal, perinatal, infant and child health outcomes. However, the prevalence and maternal and child health impacts of SBI in the Asia-Pacific region have not been well understood. This study aims to identify and summarise the existing evidence on SBI including its definition, measurement prevalence, determinants and association with adverse maternal and child health outcomes in the Asia-Pacific region.

METHODS

Five databases (MEDLINE, Scopus, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Maternity and Infant Care, and Web of Science (WoS)) will be systematically searched from September 2000 up to May 2023. Data will be extracted, charted, synthesised and summarised based on the outcomes measured, and where appropriate, meta-analysis will be performed. The risk of bias will be assessed using Joanna Briggs Institute quality appraisal. Grading of Recommendation Assessment, Development and Evaluation framework will be used to evaluate the quality of cumulative evidence from the included studies.

ETHICS AND DISSEMINATION

This review does not require ethics approval. Findings will be disseminated through peer-reviewed publications, policy briefs and conference presentations.

PROSPERO REGISTRATION NUMBER

A protocol will be registered on PROSPERO for each separate outcome before performing the review.Cite Now.

Inter-pregnancy interval and placental weight. A population based follow-up study in Norway

INTRODUCTION

We studied changes in placental weight from the first to the second delivery according to length of the inter-pregnancy interval.

METHODS

We followed all women in Norway from their first to their second successive singleton pregnancy during the years 1999-2019, a total of 271 184 women. We used data from the Medical Birth Registry of Norway and studied changes in placental weight (in grams (g)) according to the length of the inter-pregnancy. Adjustments were made for year and maternal age at first delivery, changes in the prevalence of maternal diseases (hypertension and diabetes), and a new father to the second pregnancy.

RESULTS

Mean placental weight increased from 655 g at the first delivery to 680 g at the second. The adjusted increase in placental weight was highest at inter-pregnancy intervals <6 months; 38.2 g (95 % CI 33.0g-43.4 g) versus 23.2 g (95 % CI 18.8g-27.7 g) at inter-pregnancy interval 6-17 months. At inter-pregnancy intervals ≥18 months, placental weight remained higher than at the first delivery, but was non-different from inter-pregnancy intervals 6-17 months. Also, after additional adjustment for daily smoking and body mass index in sub-samples, we found the highest increase in placental weight at the shortest inter-pregnancy interval. We estimated no difference in gestational age at delivery or placental to birthweight ratio according to inter-pregnancy interval.

DISCUSSION

Placental weight increased from the first to the second pregnancy, and the increase was most pronounced at short inter-pregnancy intervals. The biological causes and implications of such findings remain to be studied.

Birth spacing and risk of adverse pregnancy and birth outcomes: A systematic review and dose-response meta-analysis

INTRODUCTION

The association between extreme birth spacing and adverse outcomes is controversial, and available evidence is fragmented into different classifications of birth spacing.

MATERIAL AND METHODS

We conducted a systematic review of observational studies to evaluate the association between birth spacing (i.e., interpregnancy interval and interoutcome interval) and adverse outcomes (i.e., pregnancy complications, adverse birth outcomes). Pooled odds ratios (ORs) with 95% confidence intervals (CI) were calculated using a random-effects model, and the dose-response relationships were evaluated using generalized least squares trend estimation.

RESULTS

A total of 129 studies involving 46 874 843 pregnancies were included. In the general population, compared with an interpregnancy interval of 18-23 months, extreme intervals (<6 months and ≥ 60 months) were associated with an increased risk of adverse outcomes, including preterm birth, small for gestational age, low birthweight, fetal death, birth defects, early neonatal death, and premature rupture of fetal membranes (pooled OR range: 1.08-1.56; p < 0.05). The dose-response analyses further confirmed these J-shaped relationships (pnon-linear  < 0.001-0.009). Long interpregnancy interval was only associated with an increased risk of preeclampsia and gestational diabetes (pnon-linear  < 0.005 and pnon-linear  < 0.001, respectively). Similar associations were observed between interoutcome interval and risk of low birthweight and preterm birth (pnon-linear  < 0.001). Moreover, interoutcome interval of ≥60 months was associated with an increased risk of cesarean delivery (pooled OR 1.72, 95% CI 1.04-2.83). For pregnancies following preterm births, an interpregnancy interval of 9 months was not associated with an increased risk of preterm birth, according to dose-response analyses (pnon-linear  = 0.008). Based on limited evidence, we did not observe significant associations between interpregnancy interval or interoutcome interval after pregnancy losses and risk of small for gestational age, fetal death, miscarriage, or preeclampsia (pooled OR range: 0.76-1.21; p > 0.05).

CONCLUSIONS

Extreme birth spacing has extensive adverse effects on maternal and infant health. In the general population, interpregnancy interval of 18-23 months may be associated with potential benefits for both mothers and infants. For women with previous preterm birth, the optimal birth spacing may be 9 months.

The Impact of Group Prenatal Care on Interpregnancy Interval

OBJECTIVE

To evaluate whether participation in CenteringPregnancy group prenatal care is associated with decreased risk of an interpregnancy interval (IPI) ≤6 months.

STUDY DESIGN

We conducted a retrospective cohort study of women enrolled in Missouri Medicaid from 2007 to 2014 using maternal Medicaid data linked to infant birth certificate records. Inclusion criteria were women ≥11 years old, ≥1 viable singleton delivery during the study period, residency in St. Louis city or county, and ≥2 prenatal visits. The primary outcome was an IPI ≤6 months. Secondary outcomes included IPI ≤12 months, IPI ≤18 months, postpartum long-acting reversible contraception (LARC) uptake, and postpartum LARC or depot medroxyprogesterone acetate (DMPA) uptake. Data were analyzed using descriptive statistics and logistic regression. Backward stepwise logistic regression was used to adjust for potential confounders including maternal age, race, obesity, nulliparity, marital status, diabetes, hypertension, prior preterm birth, and maternal education.

RESULTS

Of the 54,968 pregnancies meeting inclusion criteria, 1,550 (3%) participated in CenteringPregnancy. CenteringPregnancy participants were less likely to have an IPI ≤6 months (adjusted odds ratio [aOR]: 0.61; 95% confidence interval [CI]: 0.47-0.79) and an IPI ≤12 months (aOR: 0.74; 95% CI: 0.62-0.87). However, there was no difference for an IPI ≤18 months (aOR: 0.89; 95% CI: 0.77-1.13). Women in CenteringPregnancy were more likely to use LARC for postpartum contraception (aOR: 1.37; 95% CI: 1.20-1.57).

CONCLUSION

Participation in CenteringPregnancy is associated with a significant decrease in an IPI ≤6 and ≤12 months and a significant increase in postpartum LARC uptake among women enrolled in Missouri Medicaid compared with women in traditional prenatal care.

KEY POINTS

· CenteringPregnancy is associated with a significant decrease in interpregnancy intervals ≤6 and ≤12 months.. · LARC uptake is significantly higher among patients participating in CenteringPregnancy.. · CenteringPregnancy participation enhances self-efficacy in making contraception decisions and promotes healthy pregnancy spacing..

The risk of perinatal mortality following short inter-pregnancy intervals-insights from 692 402 pregnancies in 113 Demographic and Health Surveys from 46 countries: a population-based analysis

BACKGROUND

Inter-pregnancy interval has been identified as a potentially modifiable risk factor to improve perinatal outcomes. We examined the WHO recommended interval of at least 24 months after a livebirth to next pregnancy, and its recommendation of waiting for at least 6 months after a pregnancy loss to improve subsequent pregnancy outcomes. We aimed to estimate the association between inter-pregnancy interval and perinatal mortality using the Demographic and Health Survey reproductive and contraceptive calendar.

METHODS

For this population-based analysis, we extracted data for pregnancies with gestational age and pregnancy outcomes from 113 publicly available Demographic and Health Surveys conducted between 2000 and 2022 in 46 countries that included a reproductive or contraceptive calendar module. The primary outcome was perinatal mortality (stillbirth and early neonatal death) while the inter-pregnancy interval was the exposure of interest, grouped into categories of less than 6 months, 6-11 months, 12-17 months, 18-23 months, and 24-59 months. The analysis was stratified by preceding pregnancy outcome (livebirths, stillbirths, or abortions). The Kaplan-Meier method and Cox proportional hazard model were used to calculate the cumulative probability of perinatal mortality and the hazard ratios (HRs).

FINDINGS

The analysis sample comprised of 692 402 pregnancies contributed by 570 145 women with a mean age of 28·4 years (SD 5·96). The overall HR of perinatal death was 2·72 (95% CI 2·52-2·93) times higher for an inter-pregnancy interval of less than 6 months compared with the WHO recommended optimal waiting time of 18-23 months following a livebirth. Overall HRs followed a context-related pattern, with the highest ratio of 2·95 (95% CI 2·67-3·25) in sub-Saharan Africa and the lowest of 1·98 (1·47-2·66) in north Africa, west Asia, and Europe. Inter-pregnancy intervals of less than 3 months, 6 months, and 12 months following stillbirth or abortion (spontaneous or induced) do not pose a higher risk for perinatal death in subsequent pregnancy.

INTERPRETATION

Our study reaffirms the WHO recommendation on optimal interval between the last livebirth and the next pregnancy of at least 24 months and avoiding pregnancy before 18 months. However, our analysis does not support the WHO recommendation of delaying the next pregnancy for at least 6 months after a pregnancy loss for improved perinatal survival.

FUNDING

None.

Effects of Short Interpregnancy Intervals on Adverse Pregnancy Outcomes - Haidian District, Beijing Municipality, China, 2017-2019

What is already known about this topic?

Interpregnancy intervals (IPIs) that are either excessively long or short have been linked with an elevated risk of adverse perinatal outcomes. Presently, no pertinent guidelines have been established in China to provide clear direction with regard to optimal IPI.

What is added by this report?

A brief interpregnancy interval may elevate the risk of miscarriage, postpartum hemorrhage, and fetal distress among expectant women.

What are the implications for public health practice?

These results could inform prenatal consultations, guiding pregnant women towards an ideal interpregnancy interval of no less than 24 months.

Breastfeeding and Hormonal Contraception: A Scoping Review of Clinical Guidelines, Professional Association Recommendations, and the Literature

Background: Postpartum contraceptive use can help prevent short-interval pregnancies, which have been associated with adverse neonatal and maternal health outcomes. Many contraceptive methods are safe for postpartum use, but patients and providers may be confused as to what impact hormonal contraception has on lactation. We performed a scoping review of the most recent U.S.-based guidelines regarding hormonal contraception on lactation to provide synthesis and recommendations to aid providers in counseling their patients. Methods: We conducted a scoping review by identifying the most recent clinical recommendations and guidelines from the Centers for Disease Control and Prevention (CDC) and three maternal and child health professional associations (American College of Obstetricians and Gynecologists [ACOG], Society for Maternal-Fetal Medicine [SMFM], and Academy of Breastfeeding Medicine [ABM]). We also reviewed the citations in these guidelines used in their development. We then conducted an updated literature review to capture studies published since the most recent systematic reviews were conducted. Results: We reviewed 1 clinical guideline from the CDC and 2 systematic reviews cited in its references, 6 professional association recommendations, and 28 publications identified through the updated literature review. Progestin-only contraceptive methods continue to demonstrate safety in breastfeeding patients, while low-quality evidence supports concerns of decreased milk supply with combined hormonal contraception. Discussion: Organizations should consider updating counseling recommendations regarding progestin-only contraceptives and lactation. Further research is needed to examine new contraceptive methods as well as the effect of hormonal contraception on lactation in the setting of preterm birth.

Understanding of Lactational Amenorrhea As a Contraceptive Method Among U.S. Pregnant Women

Introduction: The lactational amenorrhea method (LAM) of postpartum contraception is more effective than typical use of condoms or birth control pills. However, LAM may be underutilized due to incomplete perinatal counseling. Methods: We compared perceptions of the effectiveness of postpartum contraceptives including LAM among U.S.-born nulliparous pregnant women recruited using social media for a trial (NCT04601987). We used descriptive statistics to summarize data. Results: Of 760 individuals screened, 627 were invited to participate, and 451 (72%) were enrolled. Most (81%) had a college degree; 79% intended to breastfeed for at least 1 month. Only 8% believed exclusive breastfeeding reduces the chance of pregnancy "a lot" within 6 months of delivery and 2% indicated that exclusive breastfeeding is typically more effective than birth control pills or condoms. Compared with those planning to use other postpartum contraceptives, the 17% of respondents who planned to use LAM were more likely to know that breastfeeding delays return of menses (84% versus 44%, p ≤ 0.0001) and provides protection from pregnancy until menses return (54% versus 22%, p ≤ 0.0001). Although 25% of those planning to use LAM believed exclusive breastfeeding reduces pregnancy risk by "a lot," only 5% thought LAM is more effective than birth control pills and only 9% thought that it is more effective than condoms. Conclusions/Implications: First-time U.S. mothers are often unaware of breastfeeding's effects on menses and fertility. Clinicians providing counseling about postpartum contraceptive options should include more information on LAM.

Small vulnerable newborns-big potential for impact

Despite major achievements in child survival, the burden of neonatal mortality has remained high and even increased in some countries since 1990. Currently, most neonatal deaths are attributable to being born preterm, small for gestational age (SGA), or with low birthweight (LBW). Besides neonatal mortality, these conditions are associated with stillbirth and multiple morbidities, with short-term and long-term adverse consequences for the newborn, their families, and society, resulting in a major loss of human capital. Prevention of preterm birth, SGA, and LBW is thus critical for global child health and broader societal development. Progress has, however, been slow, largely because of the global community's failure to agree on the definition and magnitude of newborn vulnerability and best ways to address it, to frame the problem attractively, and to build a broad coalition of actors and a suitable governance structure to implement a change. We propose a new definition and a conceptual framework, bringing preterm birth, SGA, and LBW together under a broader umbrella term of the small vulnerable newborn (SVN). Adoption of the framework and the unified definition can facilitate improved problem definition and improved programming for SVN prevention. Interventions aiming at SVN prevention would result in a healthier start for live-born infants, while also reducing the number of stillbirths, improving maternal health, and contributing to a positive economic and social development in the society.

Provision of Postpartum Contraception Before and After the Start of the COVID-19 Pandemic in Maine

OBJECTIVE

Preliminary findings from selected health systems revealed interruptions in reproductive health care services due to the COVID-19 pandemic. We estimated changes in postpartum contraceptive provision associated with the start of the COVID-19 pandemic in Maine.

METHODS

We used the Maine Health Data Organization's All Payer Claims Database for deliveries from October 2015 through March 2021 (n = 45 916). Using an interrupted time-series analysis design, we estimated changes in provision rates of long-acting reversible contraception (LARC), permanent contraception, and moderately effective contraception within 3 and 60 days of delivery after the start of the COVID-19 pandemic. We performed 6- and 12-month analyses (April 2020-September 2020, April 2020-March 2021) as compared with the reference period (October 2015-March 2020). We used Poisson regression models to calculate level-change rate ratios (RRs) and 95% CIs.

RESULTS

The 6-month analysis found that provision of LARC (RR = 1.89; 95% CI, 1.76-2.02) and moderately effective contraception (RR = 1.51; 95% CI, 1.33-1.72) within 3 days of delivery increased at the start of the COVID-19 pandemic, while provision of LARC (RR = 0.95; 95% CI, 0.93-0.97) and moderately effective contraception (RR = 1.08; 95% CI, 1.05-1.11) within 60 days of delivery was stable. Rates of provision of permanent contraception within 3 days (RR = 0.70; 95% CI, 0.63-0.78) and 60 days (RR = 0.71; 95% CI, 0.63-0.80) decreased. RRs from the 12-month analysis were generally attenuated.

CONCLUSION

Disruptions in postpartum provision of permanent contraception occurred at the beginning of the COVID-19 pandemic in Maine. Public health policies should include guidance for contraceptive provision during public health emergencies and consider designating permanent contraception as a nonelective procedure.

Association between interpregnancy interval and maternal and neonatal adverse outcomes in women with a cesarean delivery: a population-based study

BACKGROUND

Interpregnancy interval (IPI) has been linked with several maternal and neonatal adverse events in the general population. However, the association between IPI and maternal and neonatal outcomes in women whose first delivery was by cesarean delivery is unclear. We aimed to investigate the association between IPI after cesarean delivery and the risk of maternal and neonatal adverse events.

METHODS

Women (aged ≥ 18 years) whose first delivery was cesarean delivery with 2 consecutive singleton pregnancies from the National Vital Statistics System (NVSS) database between 2017 and 2019 were included in this retrospective cohort study. In this post-hoc analysis, logistic regression analyses were used to examine IPI (≤ 11, 12-17, 18-23 [reference], 24-35, 36-59, and ≥ 60 months) in relation to the risk of repeat cesarean delivery, maternal adverse events (maternal transfusion, ruptured uterus, unplanned hysterectomy, and admission to an intensive care unit), and neonatal adverse events (low birthweight, premature birth, Apgar score at 5 min < 7, and abnormal conditions of the newborn). Stratified analysis based on age (< 35 and ≥ 35 years) and previous preterm birth.

RESULTS

We included 792,094 maternities, 704,244 (88.91%) of which underwent a repeat cesarean delivery, 5,246 (0.66%) women had adverse events, and 144,423 (18.23%) neonates had adverse events. After adjusting for confounders, compared to an IPI of 18-23 months, the IPI of ≤ 11 months [odds ratio (OR) = 1.55, 95% confidence interval (CI): 1.44-1.66], 12-17 months (OR = 1.38, 95%CI: 1.33-1.43), 36-59 months (OR = 1.12, 95%CI: 1.10-1.15), and ≥ 60 months (OR = 1.19, 95%CI: 1.16-1.22) were associated with an increased risk of repeat cesarean delivery. In terms of maternal adverse events, only IPI of ≥ 60 months (OR = 0.85, 95%CI: 0.76-0.95) was observed to be associated with decreased risk of maternal adverse events in women aged < 35 years. In analysis of neonatal adverse events, IPI of ≤ 11 months (OR = 1.14, 95%CI: 1.07-1.21), 12-17 months (OR = 1.07, 95%CI: 1.03-1.10), and ≥ 60 months (OR = 1.05, 95%CI: 1.02-1.08) were related to an increased risk of neonatal adverse events.

CONCLUSION

Both short and long IPI were associated with an increased risk of repeat cesarean delivery and neonatal adverse events, and women < 35 years may benefit from a longer IPI.

Trends in Postpartum Contraceptive Use in 20 U.S. States and Jurisdictions: The Pregnancy Risk Assessment Monitoring System, 2015-2018

INTRODUCTION

In the last decade, state and national programs and policies aimed to increase access to postpartum contraception; however, recent data on population-based estimates of postpartum contraception is limited.

METHODS

Using Pregnancy Risk Assessment Monitoring System data from 20 sites, we conducted multivariable-adjusted weighted multinomial regression to assess variation in method use by insurance status and geographic setting (urban/rural) among people with a recent live birth in 2018. We analyzed trends in contraceptive method use from 2015 to 2018 overall and within subgroups using weighted multinomial logistic regression.

RESULTS

In 2018, those without insurance had lower odds of using permanent methods (adjusted odds ratio [AOR], 0.72; 95% confidence interval [CI], 0.53-0.98), long-acting reversible contraception (LARC) (AOR, 0.67; 95% CI, 0.51-0.89), and short-acting reversible contraception (SARC) (AOR, 0.61; 95% CI, 0.47-0.81) than those with private insurance. There were no significant differences in these method categories between public and private insurance. Rural respondents had greater odds than urban respondents of using all method categories: permanent (AOR, 2.15; 95% CI, 1.67-2.77), LARC (AOR, 1.31; 95% CI, 1.04-1.65), SARC (AOR, 1.42; 95% CI, 1.15-1.76), and less effective methods (AOR, 1.38; 95% CI, 1.11-1.72). From 2015 to 2018, there was an increase in LARC use (odds ratio [OR], 1.03; 95% CI, 1.01-1.05) and use of no method (OR, 1.05; 95% CI, 1.02-1.07) and a decrease in SARC use (OR, 0.97; 95% CI, 0.95-0.99). LARC use increased among those with private insurance (OR, 1.05; 95% CI, 1.02-1.08) and in urban settings (OR, 1.04; 95% CI, 1.02-1.07), but not in other subgroups.

CONCLUSIONS

We found that those without insurance had lower odds of using effective contraception and that LARC use increased among those who had private insurance and lived in urban areas. Strategies to increase access to contraception, including increasing insurance coverage and investigating whether effectiveness of existing initiatives varies by geographic setting, may increase postpartum contraceptive use and address these differences.

Relationship Between Gender Equality and Husband Support in the Use of Postpartum Family Planning (PPFP)

Introduction

Postpartum family planning (PPFP) has been reported to decrease the risk of stunting by increasing the interval between pregnancies by 0.9 percent every month. In Indonesia, the prevalence of stunting affects 21.6% in 2022; however, it is expected that by 2024, the figure would drop to 14%.

Objective

This study aims to analyze the relationship between gender equality and husband support in the use of PPFP.

Methods

The study was conducted using a cross-sectional method and took place from August to October 2022. The participants comprised 210 women who had given birth in the first 4 to 12 months in Kulon Progo, Yogyakarta, Indonesia. The data was collected from women who visited the pediatrics and family planning clinics of community health centers from August to October 2022, using a structured questionnaire and analyzed using both the Chi-Square Test and Binary Logistic Regression Analysis.

Results

The results showed that 38.1% of the participants used PPFP. The estimated results reveal that variables such as education, husband support, gender equality, home visits, and postnatal visits (p < 0.05) influenced the implementation of postpartum contraception. While other variables such as age, occupation, income, number of children, and parity did not affect the model (p > 0.05).

Conclusion

Participating in postpartum family planning requires the husband's support and gender equality. We recommend a deliberate effort on improving postnatal mothers using postpartum family planning, one of the strategies is to increase intensive outreach to pregnant women with higher education to their husbands about the importance of postpartum family planning.

Effects of short birth interval on different forms of child mortality in Bangladesh: Application of propensity score matching technique with inverse probability of treatment weighting

BACKGROUND

The prevalence of Short Birth Interval (SBI) is higher in Low- and Middle-Income countries (LMICs), including Bangladesh. Previous studies in LMICs have estimated the effects of SBI on child mortality by comparing two unequal groups of mothers based on their socio-economic status. This approach may lead to overestimation or underestimation of the true effect of birth interval on child mortality, particularly when sample sizes are relatively small.

OBJECTIVE

We determined the effects of SBI on several forms of child mortality in Bangladesh by comparing two equal groups created by applying the propensity score matching technique.

METHODS

This study analyzed data from 5,941 mothers and 1,594 health facilities extracted from the 2017/18 Bangladesh Demographic and Health Survey and the 2017 Bangladesh Health Facility Survey. The exposure variable was SBI (defined as the interval between two subsequent births <33 months: yes, no), while the outcome variables were neonatal mortality (defined as mortality within 28 days of birth: yes, no), infant mortality (defined as mortality within 1 year of birth: yes, no), and under-five mortality (defined as mortality within 5 years of birth: yes, no). Multilevel Poisson regression based on inverse probability treatment weights was used to determine the association between exposure and outcome variables.

RESULTS

The prevalence rates of neonatal, infant, and under-five mortality were 48.8, 30.8, and 23.1 per 1000 live births, respectively. Newborns of SBI mothers were found to have a 63% higher likelihood of neonatal mortality (aPR, 1.63; 95% CI, 1.08-2.46) compared to newborns of non-SBI mothers. Furthermore, the prevalence of infant mortality and under-five mortality was 1.45 times higher (aPR, 1.45; 95% CI, 1.01-2.08) and 2.82 times higher (aPR, 2.82; 95% CI, 2.16-3.70), respectively, among babies born in a short interval of their immediately preceding sibling as compared to babies born in a normal interval of their immediately preceding sibling.

CONCLUSIONS

Findings of this study indicate that SBI is an important predictor of child mortality. Consequently, around 1 million children born in a short interval every year in Bangladesh are at risk of dying before reaching their fifth birthday. This indicates a challenge for Bangladesh to achieve the SDG 3 target to reduce neonatal and under-five mortality to 12 and 25 deaths per 1000 live births, respectively. Hence, awareness-building programs about the adverse effects of SBI and strengthening existing healthcare facilities are important.

Interpregnancy interval and preterm delivery: An empirical comparison of between-persons and within-sibship designs

BACKGROUND

Short interpregnancy interval has been associated with increased risk of preterm delivery; recent studies employing within-sibship designs suggest that this risk may be exaggerated. There are unresolved issues regarding properties of this design.

OBJECTIVES

To compare directly the results, for short intervals, of between-person and within-sibship analyses when applied to the same target population.

METHODS

Cross-sectional data are from the National Survey of Family Growth, a statistically representative survey of women and men in the USA, 2006-2015. Participants provided a complete pregnancy history including outcome, duration and ending date, enabling calculation of interval. Conventional analysis employed log-linear regression, controlling survey design, early life events, demographic variables, pregnancy intendedness, breastfeeding of the previous birth and obstetric history. Within-sibship analyses, utilising conditional log-linear regression, controlled the same variables, except those remaining static within each participant.

RESULTS

Among participants with at least three live- or stillbirths, the percentage of pregnancies in each interval, and the percent of deliveries that were preterm following that interval were 9.2%, 14.6% for <6, and 14.7%, 15.4% for 6-11, versus 12.2%, 14.7% for 18-23 months. Among participants with at least three live- or stillborn infants, those in the within-sibship analysis had a higher risk profile than comparably parous, ineligible participants. In a between-participant analysis, among those included in within-sibship models, the adjusted risk ratios (vs 18-23 months) for preterm delivery for intervals <6 and 6-11 months were 0.74 (95% CI 0.63, 0.88) and 0.85 (95% CI 0.74, 0.98). The corresponding risk ratios were 0.56 (95% CI 0.14, 2.30) and 0.49 (95% CI 0.13, 1.80) for those ineligible for the within-sibship models.

CONCLUSIONS

When comparable analyses were employed, the association between interval and preterm delivery was similar between participants included in the within-sibship analysis and those ineligible for the within-sibship analysis, but differed from those in the full cohort, perhaps due to different target populations.

Listening to patients: Opportunities to improve reproductive wellness for women with chronic conditions

OBJECTIVE

To understand how Black and Native American women with chronic conditions experience reproductive health care and identify patient-centered strategies to improve care.

STUDY SETTING AND PARTICIPANTS

We held a series of virtual focus groups between February 2021 and December 2021 with 34 women who self-identified as Black or Native American, were of childbearing age, had one or more chronic conditions, and lived in North Carolina.

STUDY DESIGN AND ANALYSIS

This qualitative, community-engaged study reviewed notes, video recordings, and graphic illustrations from the focus group sessions. Content analysis was used to iteratively identify themes. Emerging themes were reviewed by community and patient partners.

PRINCIPAL FINDINGS

There were six thematic areas that emerged on the current state of reproductive health care for people with chronic conditions: (1) lack of trust in health care providers and institutions, (2) lack of health care provider knowledge, (3) uncoordinated care, (4) need for self-advocacy, (5) provider bias, and (6) mental health strain from coping. Six approaches for care improvement emerged: (1) build on models of coordinated health care services from other conditions to design more comprehensive care clinics, (2) involve care coordinators or navigators, (3) improve educational materials for patients, (4) train clinicians to increase their capacity to be trustworthy and provide quality, equitable, person-focused care, (5) design scripts to improve clinicians' ability to talk with women about infertility, miscarriage, infant loss, and (6) all interventions and research should be co-designed to address patient priorities.

CONCLUSIONS

Engaging Black and Native American patient partners with chronic conditions in research planning is feasible, necessary, and beneficial using methods that support connection, respect, and bi-directional learning. Patient partners defined actionable strategies to improve reproductive care and wellness including comprehensive care clinics with patient navigators, trust-enhancing interventions, and better provision of reproductive health related education.

Maternal factors associated with interbirth intervals in Australia: Results from a population-based longitudinal study

BACKGROUND AND OBJECTIVE

Short and long intervals between successive births are associated with adverse birth outcomes, especially in low-income and middle-income countries, yet the birth intervals in high-income countries remain relatively understudied. The aim was to examine maternal factors associated with birth intervals in Australia.

METHODS

The sample comprised 6130 participants in the Australian Longitudinal Study on Women's Health who were born in 1973-1978, had two or more births, and responded to regular surveys between 1996 and 2018. Interbirth interval (IBI) was defined as the time between successive live births. Maternal factors were examined using accelerated failure time models.

RESULTS

For women with only two births (n = 3802), the median time to the second birth was 34.0 months (IQR 23.1, 46.2) with shorter IBI associated with higher socioeconomic status (eg, university education (31.9 months), less income stress (31.1)), and longer IBI associated with age over 35 (39.7), fair/poor health (43.0), untreated fertility problems (45.5), miscarriage (39.4), or abortion (41.0). For women with three or more births (n = 2328), the median times to the second and third births were 31.2 months (19.9, 42.1) and 36.5 months (25.3, 50.1), respectively; some factors were consistent between the first IBI and second IBI (eg, university education and being married were associated with shorter IBI), whereas income stress was associated with longer first IBI but not with second IBI.

CONCLUSIONS

Understanding maternal factors associated with birth intervals in a high-income country like Australia may enable more nuanced tailoring of guidelines for prepregnancy care.

The effects of birth spacing on early childhood development in high-income nations: A systematic review

Objective

This study aimed to systematically review the literature on the associations between birth spacing and developmental outcomes in early childhood (3-10 years of age). Studies examining the associations between interpregnancy intervals and child development outcomes during and beyond the perinatal period have not been systematically reviewed.

Methods

We searched Ovid/MEDLINE, Global Health, PsycINFO, EMBASE, CINAHL Plus, Educational Source, Research Starters, ERIC, Scopus, PubMed, Social Science Research Network database, and ProQuest's Social Sciences Databases for relevant articles published between 1 January 1989 and 25 June 2021. Studies published in English, conducted in populations residing in high-income countries with any measure of birth spacing, and child development outcomes among children aged <10 years were included. Two authors independently assessed the eligibility of studies and extracted data on the study design, setting and population, birth spacing, outcomes, and results.

Results

The search yielded 1,556 records, of which seven studies met the inclusion criteria. Five of these seven studies used birth intervals as the exposure measure. Definitions of exposure differed between the studies. Three studies reported an association between short birth spacing and poorer child development outcomes, and two studies reported an association between long birth spacing and poorer child development outcomes.

Conclusion

Currently, limited evidence suggests that the adverse effects of sub-optimal birth spacing are observable beyond infancy.

The effect of interpregnancy interval on preterm birth and low birth weight in singleton pregnancies conceived without assistance or by infertility treatments

OBJECTIVE

To determine the association of interpregnancy interval on perinatal outcomes and whether this was influenced by mode of conception.

DESIGN

Retrospective cohort.

SETTING

Centers for Disease Control and Prevention's natality national database.

PATIENT(S)

Patients who had an index singleton live birth with a preceding live birth. Index pregnancies from 2016 to 2019 were conceived with in vitro fertilization (IVF) (n = 32,829) or ovulation induction/intrauterine insemination (OI/IUI) (n = 23,016) or without assistance (n = 7,564,042).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The primary outcomes evaluated were preterm birth (<37 weeks) and low birth weight (<2,500 g). Multivariable logistic regression was performed to evaluate the association of interpregnancy intervals with perinatal outcomes stratified by mode of conception. Adjusted odds ratios and 95% confidence intervals (CIs) were presented.

RESULT(S)

Compared with the interpregnancy interval reference group of 12 to <18 months, a <12 month interpregnancy interval was associated with an increase in preterm birth (<37 weeks) for pregnancies conceived with OI/IUI or without assistance (aOR, 1.42; 95% CI, 1.16-1.74, and aOR, 1.14; 95% CI, 1.13-1.15, respectively), whereas IVF was not associated with an increase (aOR, 0.90; 95% CI, 0.77-1.04). A <12 month interpregnancy interval was associated with an increase in low birth weight for pregnancies conceived with IVF or OI/IUI or without assistance (aOR, 1.34; 95% CI, 1.09-1.64; aOR, 1.33; 95% CI, 1.01-1.76; and aOR, 1.26; 95% CI, 1.24-1.27, respectively).

CONCLUSION(S)

An interpregnancy interval of at least 12 months reduces adverse perinatal outcomes for pregnancies conceived with and without infertility treatment.

Interconception Health: Improving Equitable Access to Pregnancy Planning

Challenges remain with the implementation of preconception care, as many women do not plan their pregnancies and clinicians do not initiate preconception consultations. However, the interconception period may present a more opportune time to address health issues that impact on pregnancy outcomes and may influence future conceptions. It is also an important time to focus on pregnancy complications that may influence a person's health trajectory. This review discusses the evidence pointing to a need for greater attention on interconception health and focuses on five areas of care that may be particularly important in affecting equitable access to good care before a subsequent pregnancy: interpregnancy intervals, contraception, weight, nutrition, and gestational diabetes follow-up. Several programs internationally have developed models of care for interconception health and this review presents one such model developed in the United States that explicitly seeks to reach vulnerable populations of women who may otherwise not receive preconception care.

Birth Spacing and Health and Socioeconomic Outcomes Across the Life Course: Evidence From the Utah Population Database

The relationship between birth interval length and child outcomes has received increased attention in recent years, but few studies have examined offspring outcomes across the life course in North America. We use data from the Utah Population Database to examine the relationship between birth intervals and short- and long-term outcomes: preterm birth, low birth weight (LBW), infant mortality, college degree attainment, occupational status, and adult mortality. Using linear regression, linear probability models, and survival analysis, we compare results from models with and without sibling comparisons. Children born after a birth interval of 9-12 months have a higher probability of LBW, preterm birth, and infant mortality both with and without sibling comparisons; longer intervals are associated with a lower probability of these outcomes. Short intervals before the birth of the next youngest sibling are also associated with LBW, preterm birth, and infant mortality both with and without sibling comparisons. This pattern raises concerns that the sibling comparison models do not fully adjust for within-family factors predicting both spacing and perinatal outcomes. In sibling comparison analyses considering long-term outcomes, not even the very shortest birth intervals are negatively associated with educational or occupational outcomes or with long-term mortality. These findings suggest that extremely short birth intervals may increase the probability of poor perinatal outcomes but that any such disadvantages disappear over the extended life course.

Interpregnancy Interval and Birth Outcomes: A Propensity Matching Study in the California Population

INTRODUCTION

Previous studies that used traditional multivariable and sibling matched analyses to investigate interpregnancy interval (IPI) and birth outcomes have reached mixed conclusions about a minimum recommended IPI, raising concerns about confounding. Our objective was to isolate the contribution of interpregnancy interval to the risk for adverse birth outcomes using propensity score matching.

METHODS

For this retrospective cohort study, data were drawn from a California Department of Health Care Access and Information database with linked vital records and hospital discharge records (2007-2012). We compared short IPIs of < 6, 6-11, and 12-17 months to a referent IPI of 18-23 months using 1:1 exact propensity score matching on 13 maternal sociodemographic and clinical factors. We used logistic regression to calculate the odds of preterm birth, early-term birth, and small for gestational age (SGA).

RESULTS

Of 144,733 women, 73.6% had IPIs < 18 months, 5.5% delivered preterm, 27.0% delivered early-term, and 6.0% had SGA infants. In the propensity matched sample (n = 83,788), odds of preterm birth were increased among women with IPI < 6 and 6-11 months (OR 1.89, 95% CI 1.71-2.0; OR 1.22, 95% CI 1.13-1.31, respectively) and not with IPI 12-17 months (OR 1.01, 95% CI 0.94-1.09); a similar pattern emerged for early-term birth. The odds of SGA were slightly elevated only for intervals < 6 months (OR 1.10, 95% CI 1.00-1.20, p < .05).

DISCUSSION

This study demonstrates a dose response association between short IPI and adverse birth outcomes, with no increased risk beyond 12 months. Findings suggest that longer IPI recommendations may be overly proscriptive.

Incorporating Black women’s perspectives into long-acting reversible contraception implementation

Objective

To study urban, predominantly Black women’s expressed opinions and beliefs related to the use of contraceptives to better inform implementation strategies designed to increase the use of highly effective contraceptives among minoritized and low-income women.

Design

Focus group interviews with women, in conjunction with a community-based organization providing programs for underserved women with a mission of improved women and infant health.

Setting

Focus groups were conducted, and women were recruited from clinical sites in predominantly African American urban neighborhoods in a southeastern US city.

Patient(s)

Self-identified 18–35-year-old women recruited from clinical sites in the urban core of the city with an 80% African American population.

Intervention(s)

No interventions tested.

Main Outcome Measure(s)

Black women’s opinions and concerns about contraception.

Results

Key insights from the focus group results for healthcare providers include the following: the importance of framing discussions with patients within the context of the patients’ goals; need to acknowledge and respect the support systems that women rely on for child birthing and childcare; recognition of the clinician’s role as a trusted and respected source of information; and need to understand and be prepared to address much of the inaccurate and misleading information that can interfere with the patients’ optimal choices for contraception.

Conclusions

A critical component for applying the implementation science theory to increase the use of evidence-based practices, such as implementation of highly effective contraceptives, requires understanding women’s perspectives of the factors influencing their decisions to use highly effective contraceptives. This study provides important insights into the following: the potential barriers inherent in minoritized women’s concerns about contraceptives and how these insights can inform implementation strategies such as patient-centered counseling and education to overcome those barriers.

Short interpregnancy interval: circumstance or choice?

INTRODUCTION

Despite the knowledge of pregnancy risks attributable to inadequate birth spacing, over one-third of pregnancies occur within 18 months of a preceding birth. In this qualitative study we sought to interview women with a short interpregnancy interval (sIPI) to explore their knowledge of contraception and birth spacing and their experience of counselling on these themes.

METHODS

We conducted in-depth interviews with women with a sIPI (live-birth less than 18 months prior to conception of current pregnancy) at Royal Prince Alfred Hospital and Canterbury Hospital in Sydney, Australia. Women were recruited at the second antenatal visit or day 3 postpartum. Interviews were recorded and transcribed. The six-phase thematic analysis framework described by Braun and Clarke was used to perform qualitative data analysis.

RESULTS

Twenty women were interviewed (IPI range: 3-18 months). The three central themes that arose were that perceptions of IPIs are shaped by individual circumstances, a lack of information from healthcare providers (HCPs) on IPI and contraception limited women's ability to make informed decisions, and that reproductive life planning is an important element of pregnancy care.

CONCLUSIONS

In this study, women with a sIPI did not feel informed about birth spacing, had poor knowledge of reliable contraceptives, and remained at risk of further closely spaced pregnancies. There was a desire among women with a sIPI to receive clear and consistent education on these topics. HCPs need to do more to educate women in the antenatal and postnatal period to help them space their pregnancies appropriately.

Association of Medicaid Reimbursement for Immediate Postpartum Long-acting Reversible Contraception With Infant Birth Outcomes

IMPORTANCE

Together, preterm birth and low birth weight are the second-leading cause of infant mortality in the US and occur disproportionately among Medicaid-paid births and among the infants of Black birthing persons. In 2012, South Carolina's Medicaid program began to reimburse hospitals for immediate postpartum long-acting reversible contraception (LARC) separately from the global maternity payment.

OBJECTIVE

To examine the association between South Carolina's policy change and infant health.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study using a difference-in-differences analysis included individuals with a South Carolina Medicaid-paid childbirth between January 2009 and December 2015. Data were analyzed from December 2020 to July 2021.

EXPOSURES

Medicaid-paid childbirth after March 2012 in South Carolina hospitals that had implemented the policy.

MAIN OUTCOMES AND MEASURES

Immediate postpartum LARC uptake, subsequent birth within 4 years, subsequent short-interval birth, days to subsequent birth, subsequent preterm, and low-birth-weight birth within 4 years.

RESULTS

The study sample included 186 953 Medicaid-paid births between January 2009 and December 2015 in South Carolina (81 110 births from 2009 to 2011, 105 843 births from 2012 to 2015, and 46 414 births in exposure hospitals). The policy was associated with an absolute 5.6-percentage point (95% CI, 3.7-7.4) increase in the probability of receiving an immediate postpartum LARC overall, with significantly larger effects for non-Hispanic Black individuals than non-Hispanic White individuals (difference in coefficients 3.54; 95% CI, 1.35-5.73; P = .002). The policy was associated with a 0.4-percentage point (95% CI, -0.7 to -0.1) decrease in the probability of subsequent preterm birth and a 0.3-percentage point (95% CI, -0.7 to 0) decrease in the probability of subsequent low birth weight. No significant difference in the association between the policy and preterm birth or low-birth-weight birth between non-Hispanic Black and non-Hispanic White individuals was found. The policy was associated with a 0.6-percentage point (95% CI, -1.2 to -0.1) decrease in the probability of short-interval birth and a 27-day (95% CI, 11-44) increase in days to next birth among non-Hispanic Black individuals. The policy was associated with a significant decrease in the probability of a subsequent birth overall; however, confidence in this result is attenuated somewhat by nonparallel trends for this outcome before the policy change.

CONCLUSIONS AND RELEVANCE

Findings of this cohort study suggest policies increasing access to immediate postpartum LARC may improve birth outcomes but should be accompanied by other policy efforts to reduce inequity in these outcomes.

The confounder matrix: A tool to assess confounding bias in systematic reviews of observational studies of etiology

Systematic reviews and meta-analyses are essential for drawing conclusions regarding etiologic associations between exposures or interventions and health outcomes. Observational studies comprise a substantive source of the evidence base. One major threat to their validity is residual confounding, which may occur when component studies adjust for different sets of confounders, fail to control for important confounders, or have classification errors resulting in only partial control of measured confounders. We present the confounder matrix-an approach for defining and summarizing adequate confounding control in systematic reviews of observational studies and incorporating this assessment into meta-analyses. First, an expert group reaches consensus regarding the core confounders that should be controlled and the best available method for their measurement. Second, a matrix graphically depicts how each component study accounted for each confounder. Third, the assessment of control adequacy informs quantitative synthesis. We illustrate the approach with studies of the association between short interpregnancy intervals and preterm birth. Our findings suggest that uncontrolled confounding, notably by reproductive history and sociodemographics, resulted in exaggerated estimates. Moreover, no studies adequately controlled for all core confounders, so we suspect residual confounding is present, even among studies with better control. The confounder matrix serves as an extension of previously published methodological guidance for observational research synthesis, enabling transparent reporting of confounding control and directly informing meta-analysis so that conclusions are drawn from the best available evidence. Widespread application could raise awareness about gaps across a body of work and allow for more valid inference with respect to confounder control.

Preconception exposures and adverse pregnancy, birth and postpartum outcomes: Umbrella review of systematic reviews

BACKGROUND

Preconception exposures have been associated with adverse pregnancy, birth and postpartum outcomes. However, the reports, statements and guidelines of national and international health organisations vary in what they recommend individuals should monitor, avoid, reduce or practise in the preconception period.

OBJECTIVES

To synthesise and evaluate the evidence across systematic reviews for associations between exposures before conception and adverse pregnancy, birth and postpartum outcomes.

DATA SOURCES

MEDLINE, Embase, Epistemonikos (to May 2020) and reference lists of included reviews, without language or date restrictions.

STUDY SELECTION, DATA EXTRACTION AND SYNTHESIS

Systematic literature reviews of observational and/or interventional studies reporting associations between preconception exposures in women and/or men of reproductive age and pregnancy, birth or postpartum health outcomes were included. The methodological quality of reviews and the certainty of the evidence underlying each exposure-outcome association were assessed using AMSTAR 2 and the GRADE approach.

RESULTS

We identified 53 eligible reviews reporting 205 unique exposure-outcome associations. Methodological quality was generally low with only two reviews rated as 'high' quality and two as 'moderate'. We found high-certainty, randomised trial evidence that maternal folate supplementation reduces the risk of neural tube defects and anomaly-related terminations. Moderate-certainty, observational evidence was found that maternal physical activity is associated with reduced risk of pre-eclampsia and gestational diabetes, and that paternal age of ≥40 years and maternal body mass index (BMI) and interpregnancy weight gain are associated with increased risk of various adverse pregnancy and birth outcomes. Low- and very low-certainty evidence was found for other associations.

CONCLUSIONS

Clinicians and policymakers can be confident that maternal folate supplementation should be encouraged during the preconception period. There is moderate certainty in the evidence base that maternal physical activity, BMI and interpregnancy weight gain and advanced paternal age are important preconception considerations. High-quality research is required to better understand other exposure-outcome associations.

Impact of Group Prenatal Care on Contraceptive Use at Twelve Weeks Postpartum

OBJECTIVES

To compare the prevalence of highly effective contraceptive use by 12 weeks postpartum among participants of Centering Pregnancy®, a model of group prenatal care (GPC), and traditional prenatal care (TPC), and to investigate differences in contraceptive method choice by type of prenatal care.

METHODS

We performed a retrospective review of all eligible patients who participated in GPC (n = 143) and a random sample of patients participating in TPC (n = 290) who followed up at our institution within 12 weeks of delivery. Our primary outcome was the proportion of participants using a highly effective contraceptive method within 12 weeks postpartum. Contraceptives were classified in tiers (Tier 1, long-acting reversible and permanent contraception; Tier 2, oral contraceptive pills, transdermal patch, vaginal ring, or injection; Tier 3, barrier and fertility awareness methods, withdrawal, spermicide; and no method). Tier 1 and Tier 2 methods were considered highly effective.

RESULTS

The prevalence of highly effective contraceptive use by 12 weeks postpartum was 63.6% (91 of 143) and 63.1% (183 of 290) among participants in GPC and TPC, respectively (p = 0.99). We found no difference in Tier 1 versus other method use (adjusted odds ratio (aOR) 1.05, 95% CI 0.95-1.15, p = 0.34) or Tier 2 versus other method use between groups (aOR 0.98, 95% CI 0.89-1.08, p = 0.69), in a multivariable model controlling for demographic and clinical factors.

CONCLUSIONS FOR PRACTICE

The prevalence of highly effective contraceptive use at 12 weeks postpartum was not different between GPC and TPC participants in this study. GPC was not associated with increased use of Tier 1 or Tier 2 contraceptive methods.

Preconception Hemoglobin Concentration and Risk of Low Birth Weight and Small-for-Gestational-Age: A Large Prospective Cohort Study in China

Less is known about the impact of maternal preconception anemia on birth outcomes. We aimed to examine associations between preconception hemoglobin (Hb) concentrations with risk of low birth weight (LBW) and small-for-gestational-age (SGA). This study was from a large population-based prospective cohort in China and included 124,725 women with singleton live births delivered at gestational ages of 28–45 weeks who were registered before pregnancy. Maternal Hb concentrations were measured during registration, and other health-related information was recorded prospectively. Logistic regression was used to evaluate the associations between preconception Hb concentrations with risk of LBW and SGA, adjusting for potential confounders. The results showed women with preconception anemia accounted for 22.28%. The incidences of LBW/SGA were 2.37%/6.30% among anemic women, and 2.01%/5.48% among non-anemic women, respectively. Preconception mild anemia increased by 17% (95% confidence interval (CI): 1.06, 1.28) and 14% (95% CI: 1.07, 1.21) the risk for LBW and SGA, while moderate-to-severe anemia had no significant association with LBW and SGA. Compared with the 120–129 g/L group, a U-shaped association was observed between preconception Hb concentrations with LBW and SGA. In conclusion, not only maternal anemia but also elevated Hb concentrations before pregnancy contribute to an increased risk of LBW and SGA.

Interpregnancy interval and prevalence of selected birth defects: A multistate study

BACKGROUND

Both short and long interpregnancy intervals (IPIs) have been associated with adverse birth outcomes. We undertook a multistate study to describe the prevalence of selected birth defects by IPI.

METHODS

We obtained data from nine population-based state birth defects registries for singleton live births in 2000-2009 among mothers with a previous live birth identified through birth certificates. IPI was calculated as the difference between prior birthdate and start of the current pregnancy (conception date). We estimated prevalence of selected defects per 10,000 live births and prevalence ratios (PRs) with 95% confidence intervals (CIs) overall and stratified by maternal age at previous birth and race/ethnicity. Primary analyses focused on short IPI < 6 months and long IPI ≥ 60 months compared to 18-23 months (referent). Sensitivity analyses limited to active-surveillance states and those with<10% missing IPI.

RESULTS

Among 5,147,962 eligible births, 6.3% had short IPI while 19.8% had long IPI. Compared to referent, prevalence with short IPI was elevated for gastroschisis (3.7, CI: 3.0-4.5 vs. 2.0, CI: 1.6-2.4) and with both short and long IPI for tetralogy of Fallot (short: 3.4, 2.8-4.2 long: 3.8, 3.4-4.3 vs. 2.7, 2.3-3.2) and cleft lip ± palate (short: 9.9, 8.8-11.2 long: 9.2, 8.5-9.8 vs. 8.4, 7.6-9.2). Stratified analyses identified additional associations, including elevated prevalence of anencephaly with short IPI in younger mothers and limb defects with long IPI in those ages 25-34 at prior birth. Sensitivity analyses showed similar results.

CONCLUSION

In this population-based study, we observed increased prevalence of several birth defects with short and long IPI.

Interpregnancy intervals and adverse birth outcomes in high-income countries: An international cohort study

BACKGROUND

Most evidence for interpregnancy interval (IPI) and adverse birth outcomes come from studies that are prone to incomplete control for confounders that vary between women. Comparing pregnancies to the same women can address this issue.

METHODS

We conducted an international longitudinal cohort study of 5,521,211 births to 3,849,193 women from Australia (1980-2016), Finland (1987-2017), Norway (1980-2016) and the United States (California) (1991-2012). IPI was calculated based on the time difference between two dates-the date of birth of the first pregnancy and the date of conception of the next (index) pregnancy. We estimated associations between IPI and preterm birth (PTB), spontaneous PTB, and small-for-gestational age births (SGA) using logistic regression (between-women analyses). We also used conditional logistic regression comparing IPIs and birth outcomes in the same women (within-women analyses). Random effects meta-analysis was used to calculate pooled adjusted odds ratios (aOR).

RESULTS

Compared to an IPI of 18-23 months, there was insufficient evidence for an association between IPI <6 months and overall PTB (aOR 1.08, 95% CI 0.99-1.18) and SGA (aOR 0.99, 95% CI 0.81-1.19), but increased odds of spontaneous PTB (aOR 1.38, 95% CI 1.21-1.57) in the within-women analysis. We observed elevated odds of all birth outcomes associated with IPI ≥60 months. In comparison, between-women analyses showed elevated odds of adverse birth outcomes for <12 month and >24 month IPIs.

CONCLUSIONS

We found consistently elevated odds of adverse birth outcomes following long IPIs. IPI shorter than 6 months were associated with elevated risk of spontaneous PTB, but there was insufficient evidence for increased risk of other adverse birth outcomes. Current recommendations of waiting at least 24 months to conceive after a previous pregnancy, may be unnecessarily long in high-income countries.

Short interpregnancy interval and pregnancy outcomes: How important is the timing of confounding variable ascertainment?

BACKGROUND

Estimation of causal effects of short interpregnancy interval on pregnancy outcomes may be confounded by time-varying factors. These confounders should be ascertained at or before delivery of the first ("index") pregnancy, but are often only measured at the subsequent pregnancy.

OBJECTIVES

To quantify bias induced by adjusting for time-varying confounders ascertained at the subsequent (rather than the index) pregnancy in estimated effects of short interpregnancy interval on pregnancy outcomes.

METHODS

We analysed linked records for births in British Columbia, Canada, 2004-2014, to women with ≥2 singleton pregnancies (n = 121 151). We used log binomial regression to compare short (<6, 6-11, 12-17 months) to 18-23-month reference intervals for 5 outcomes: perinatal mortality (stillbirth and neonatal death); small for gestational age (SGA) birth and preterm delivery (all, early, spontaneous). We calculated per cent differences between adjusted risk ratios (aRR) from two models with maternal age, low socio-economic status, body mass index, and smoking ascertained in the index pregnancy and the subsequent pregnancy. We considered relative per cent differences <5% minimal, 5%-9% modest, and ≥10% substantial.

RESULTS

Adjustment for confounders measured at the subsequent pregnancy introduced modest bias towards the null for perinatal mortality aRRs for <6-month interpregnancy intervals [-9.7%, 95% confidence interval [CI] -15.3, -6.2). SGA aRRs were minimally biased towards the null (-1.1%, 95% CI -2.6, 0.8) for <6-month intervals. While early preterm delivery aRRs were substantially biased towards the null (-10.4%, 95% CI -14.0, -6.6) for <6-month interpregnancy intervals, bias was minimal for <6-month intervals for all preterm deliveries (-0.6%, 95% CI -2.0, 0.8) and spontaneous preterm deliveries (-1.3%, 95% CI -3.1, 0.1). For all outcomes, bias was attenuated and minimal for 6-11-month and 12-17-month interpregnancy intervals.

CONCLUSION

These findings suggest that maternally linked pregnancy data may not be needed for appropriate confounder adjustment when studying the effects of short interpregnancy interval on pregnancy outcomes.

Increased Risk of ADHD at Short and Long Interpregnancy Intervals in a National Birth Cohort

BACKGROUND

Short or long interpregnancy interval (IPI) may adversely impact conditions for foetal development. Whether attention deficit hyperactivity disorder (ADHD) is related to IPI has been largely unexplored.

OBJECTIVES

To examine the association between IPI and ADHD in a large, population-based Finnish study.

METHODS

All children born in Finland between 1991 and 2005 and diagnosed with ADHD (ICD-9 314x or ICD-10 F90.x) from 1995 to 2011 were identified using data from linked national registers. Each subject with ADHD was matched to 4 controls based on sex, date of birth, and place of birth. A total of 9564 subjects with ADHD and 34,479 matched controls were included in analyses. IPI was calculated as the time interval between sibling birth dates minus the gestational age of the second sibling. The association between IPI and ADHD was determined using conditional logistic regression and adjusted for potential confounders.

RESULTS

Relative to births with an IPI of 24 to 59 months, those with the shortest IPI (<6 months) had an increased risk of ADHD (odds ratio [OR] 1.30, 95% confidence interval (CI) 1.12, 1.51) and the ORs for the longer IPI births (60-119 months and ≥120 months) were 1.12 (95% CI 1.02, 1.24) and 1.25 (95% CI 1.08, 1.45), respectively. The association of longer IPI with ADHD was attenuated by adjustment for maternal age at the preceding birth, and comorbid autism spectrum disorders did not explain the associations with ADHD.

CONCLUSIONS

The risk of ADHD is higher among children born following short or long IPIs although further studies are needed to explain this association.