A Population-Based Matched-Sibling Analysis Estimating the Associations Between First Interpregnancy Interval and Birth Outcomes.
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SUBMITTER: Regan AK
PROVIDER: S-EPMC6321799 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:ImportanceMany studies have reported an association of interpregnancy interval (IPI) between 2 consecutive births with adverse birth outcomes in low- and middle-income countries. However, most of these studies ignore the implications of some unmeasured confounders.ObjectiveTo explore the association of IPI with adverse perinatal outcomes.Design, setting, and participantsThis large-scale cohort study used the Guangdong Provincial Women and Children Health Information System in Guangdong Province, China, to obtain birth data recorded between January 1, 2014, and December 31, 2020. Matched-sibling design was used. The final cohort included first-born and second-born sibling pairs delivered by mothers who were permanent residents of Guangdong Province.ExposuresThe exposure variable was IPI, which was categorized as follows: less than 6, 6 to 11, 12 to 17, 18 to 23, 24 to 29, 30 to 35, and 36 or more months.Main outcomes and measuresThe outcome variables were adverse birth outcomes: preterm birth (PTB, gestational age <37 weeks), low birth weight (LBW, <2500 g), and small for gestational age (SGA). Adjusted odds ratio (OR) and interaction odds ratio (IOR) associated with IPI were calculated.ResultsThe study consisted of 725 392 sibling pairs of multiparous mothers. Among these mothers, 718 111 (99.0%) were aged 20 to 34 years, and 715 583 (98.7%) were of Han Chinese ethnicity. Unmatched analysis showed that a short IPI of less than 6 months was associated with higher risks of PTB (adjusted OR, 1.96; 95% CI, 1.87-2.06), LBW (adjusted OR, 1.88; 95% CI, 1.79-1.98), and SGA (adjusted OR, 1.34; 95% CI, 1.30-1.38) compared with an IPI of 18 to 23 months. These associations were attenuated in the matched-sibling analysis. An association of short IPI (<6 months) with PTB (adjusted IOR, 1.40; 95% CI, 1.30-1.51), LBW (adjusted IOR, 1.30; 95% CI, 1.21-1.40), and SGA (adjusted IOR, 1.16; 95% CI, 1.11-1.22) remained in the matched analysis. For IPI of 36 months or more, the odds of PTB (adjusted OR, 1.08; 95% CI, 1.03-1.14) and LBW (adjusted OR, 1.13; 95% CI, 1.07-1.19) in the unmatched analysis were also greater than the reference interval (18-23 months), but not for SGA (adjusted OR, 0.96; 95% CI, 0.93-0.99). Associations between a long IPI (≥36 months) and PTB (adjusted IOR, 1.10; 95% CI, 1.02-1.19) and LBW (adjusted IOR, 1.16; 95% CI, 1.07-1.26) remained through the sibling comparisons.Conclusions and relevanceResults of this study indicated that mothers with a short (<6 months) or long (≥36 months) IPI had greater odds of adverse birth outcomes. The findings may inform family planning policies and guide individuals and families who are planning for another pregnancy in China.
| S-EPMC9194661 | biostudies-literature
Project description:IntroductionPrevious 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.MethodsFor 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).ResultsOf 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).DiscussionThis 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.
| S-EPMC9023393 | biostudies-literature
Project description:BACKGROUND:Several studies have examined the association between IPI and birth outcomes, but few have explored the association between interpregnancy interval (IPI) and postnatal outcomes. OBJECTIVE:We examined the association between IPI and injury-related infant mortality, a leading cause of postneonatal mortality. METHODS:We used 2011-2015 US period-linked birth-infant death vital statistics data to generate a multiyear birth cohort of non-first-born singleton births (N = 9 782 029). IPI was defined as the number of months between a live birth and the start of the pregnancy leading to the next live birth. Causes of death in the first year of life were identified using ICD-10 codes. Hazard ratios (HR) for IPI categories were estimated using Cox proportional hazards models adjusted for birth order, county poverty level, and maternal characteristics (marital status, race/ethnicity, education, age at previous birth). RESULTS:After adjustment, overall infant mortality (48.1 per 10 000 births) was higher for short and long IPIs compared with IPI 18-23 months (reference): <6, aHR 1.61, 95% CI 1.54, 1.68; 6-11, aHR 1.22, 95% CI 1.17, 1.26; and 60+ months, aHR 1.12, 95% CI 1.08, 1.16. In comparison, the risk of injury-related infant mortality (4.4 per 10 000 births) decreased with longer IPIs: <6, aHR 1.77, 95% CI 1.55, 2.01; 6-11, aHR 1.41, 95% CI 1.25, 1.59; 12-17, aHR 1.25, 95% CI 1.10, 1.41; 24-59, aHR 0.78, 95% CI 0.69, 0.87; and 60+ months, aHR 0.55, 95% CI 0.48, 0.62. CONCLUSION:Unlike overall infant mortality, injury-related infant mortality decreased with IPI length. While injury-related deaths are rare, these patterns suggest that the timing between births may be a marker of risk for fatal infant injuries. The first year postpartum may be an ideal time for the delivery of evidence-based injury prevention programmes as well as family planning services.
| S-EPMC6913028 | biostudies-literature
Project description:OBJECTIVE:To examine associations among interpregnancy interval, the duration from the preceding birth to the conception of the next-born index child, and adverse birth outcomes using designs that adjust for measured and unmeasured factors. METHODS:In this prospective cohort study, we used population-based Swedish registries from 1973 to 2009 to estimate the associations between interpregnancy interval (referent 18-23 months) and adverse birth outcomes (ie, preterm birth [less than 37 weeks of gestation], low birth weight [LBW; less than 2,500 g], small for gestational age [SGA; greater than 2 SDs below average weight for gestational age]). Analyses included cousin and sibling comparisons and postbirth intervals (ie, the interval between secondborn and thirdborn offspring predicting secondborn outcomes) to address unmeasured familial confounding. RESULTS:Traditional cohort-wide analyses showed higher odds of preterm birth (adjusted odds ratio [OR] 1.51, 99% CI 1.39-1.63, 5.99% preterm births]) and LBW (adjusted OR 1.25, 99% CI 1.13-1.39, 3.32% LBW) after a short interpregnancy interval (0-5 months) compared with offspring born after an interpregnancy interval of 18-23 months (3.21% preterm births, 1.92% LBW). Except for preterm birth (adjusted OR 1.72, 99% CI 1.26-2.35), associations were attenuated in cousin comparisons. A small association between a short interpregnancy interval and preterm birth remained in sibling comparisons (adjusted OR 1.22, 99% CI 1.11-1.35), but associations with LBW (adjusted OR 0.83, 99% CI 0.74-0.94) and SGA (adjusted OR 0.74, 99% CI 0.64-0.85) reversed direction. For pregnancy intervals of 60 months or more, odds of preterm birth (adjusted OR 1.51, 99% CI 1.43-1.60, 5.07% preterm births), LBW (adjusted OR 1.61, 99% CI 1.50-1.73, 3.43% low-birth-weight births), and SGA (adjusted OR 1.54, 99% CI 1.42-1.66, 2.49% SGA births) were also higher when compared with the reference interval (1.53% SGA). Associations between long interpregnancy interval and adverse birth outcomes remained through cousin and sibling comparisons. Postbirth interval analyses showed familial confounding is present for short interpregnancy intervals, but supported independent associations for long interpregnancy intervals. CONCLUSION:Familial confounding explains most of the association between a short interpregnancy interval and adverse birth outcomes, whereas associations with long interpregnancy intervals were independent of measured and unmeasured factors.
| S-EPMC5783305 | biostudies-literature
Project description:BackgroundResearch documents social and economic antecedents of adverse birth outcomes, which may include involuntary job loss. Previous work on job loss and adverse birth outcomes, however, lacks high-quality individual data on, and variation in, plausibly exogenous job loss during pregnancy and therefore cannot rule out strong confounding.MethodsWe analysed unique linked registries in Denmark, from 1980 to 2017, to examine whether a father's involuntary job loss during his spouse's pregnancy increases the risk of a low-weight (i.e. <2500 grams) and/or preterm (i.e. <37 weeks of gestational age) birth. We applied a matched-sibling design to 743 574 sibling pairs.ResultsResults indicate an increased risk of a low-weight birth among infants exposed in utero to fathers' unexpected job loss [odds ratio (OR) = 1.37, 95% confidence interval (CI): 1.07, 1.75]. Sex-specific analyses show that this result holds for males (OR = 1.70, 95% CI: 1.14, 2.53) but not females (OR = 1.24, 95% CI: 0.80, 1.91). We find no relation with preterm birth.ConclusionsFindings support the inference that a father's unexpected job loss adversely affects the course of pregnancy, especially among males exposed in utero.
| S-EPMC9189955 | biostudies-literature
Project description:A short interpregnancy interval (IPI) is a risk factor for preterm delivery among women of reproductive age. As limited data exist concerning adolescents, we aimed to examine the association between short IPIs and preterm birth among adolescents using a majority of US births. Using 2007-2008 US natality data, we assessed the relationship between IPIs <3, 3-5, 6-11, and 12-17 months and moderately (32-36 weeks) and very (<32 weeks) preterm singleton live births among mothers <20 years, relative to IPIs 18-23 months. Adjusted odds ratios (aORs) and 95 % confidence intervals (95 % CIs) adjusted for maternal race, age, previous preterm deliveries, marital status, smoking and prenatal care were determined from a multivariable multinomial logistic regression model. In 2007-2008, there were 85,077 singleton live births to women aged <20 who had one previous live birth, 69 % of which followed IPIs ≤18 months. Compared with IPIs 18-23 months, short IPIs were associated with moderately preterm birth for IPIs <3 months (aOR 1.89, 95 % CI 1.70-2.10), 3-5 months (aOR 1.33, 95 % CI 1.22-1.47), and 6-12 months (aOR 1.11, 95 % CI 1.02-1.21). IPIs <3 and <6 months were also associated with very preterm birth, with aORs of 2.52 (95 % CI 1.98-3.22) and 1.68 (95 % CI 1.35-2.10) respectively. Many adolescent mothers with repeat births have short IPIs, and shorter IPIs are associated with preterm birth in a dose-dependent fashion. Increasing adolescent mothers' use of effective contraception postpartum can address both unintended adolescent births and preterm birth.
| S-EPMC5547434 | biostudies-other
Project description:ObjectiveTo re-evaluate the causal effect of interpregnancy interval on adverse birth outcomes, on the basis that previous studies relying on between mother comparisons may have inadequately adjusted for confounding by maternal risk factors.DesignRetrospective cohort study using conditional logistic regression (matching two intervals per mother so each mother acts as her own control) to model the incidence of adverse birth outcomes as a function of interpregnancy interval; additional unconditional logistic regression with adjustment for confounders enabled comparison with the unmatched design of previous studies.SettingPerth, Western Australia, 1980-2010.Participants40 441 mothers who each delivered three liveborn singleton neonates.Main outcome measuresPreterm birth (<37 weeks), small for gestational age birth (<10th centile of birth weight by sex and gestational age), and low birth weight (<2500 g).ResultsWithin mother analysis of interpregnancy intervals indicated a much weaker effect of short intervals on the odds of preterm birth and low birth weight compared with estimates generated using a traditional between mother analysis. The traditional unmatched design estimated an adjusted odds ratio for an interpregnancy interval of 0-5 months (relative to the reference category of 18-23 months) of 1.41 (95% confidence interval 1.31 to 1.51) for preterm birth, 1.26 (1.15 to 1.37) for low birth weight, and 0.98 (0.92 to 1.06) for small for gestational age birth. In comparison, the matched design showed a much weaker effect of short interpregnancy interval on preterm birth (odds ratio 1.07, 0.86 to 1.34) and low birth weight (1.03, 0.79 to 1.34), and the effect for small for gestational age birth remained small (1.08, 0.87 to 1.34). Both the unmatched and matched models estimated a high odds of small for gestational age birth and low birth weight for long interpregnancy intervals (longer than 59 months), but the estimated effect of long interpregnancy intervals on the odds of preterm birth was much weaker in the matched model than in the unmatched model.ConclusionThis study questions the causal effect of short interpregnancy intervals on adverse birth outcomes and points to the possibility of unmeasured or inadequately specified maternal factors in previous studies.
| S-EPMC4137882 | biostudies-literature
Project description:OBJECTIVE:To compare associations between interpregnancy intervals (IPIs) and adverse perinatal outcomes in deliveries following IVF with deliveries following spontaneous conception or other (non-IVF) fertility treatments. DESIGN:Cohort using linked birth certificate and assisted reproductive technology surveillance data from Massachusetts and Michigan. SETTING:Not applicable. PATIENT(S):1,225,718 deliveries. INTERVENTION(S):None. MAIN OUTCOMES MEASURE(S):We assessed associations between IPI and preterm birth (PTB), low birth weight (LBW), and small for gestational age (SGA) according to live birth or nonlive pregnancy outcome in the previous pregnancy. RESULT(S):In IVF deliveries following previous live birth, risk of PTB was 22.2% for IPI 12 to <24 months (reference); risk of PTB was higher for IPI <12 months (adjusted relative risk [aRR] 1.24, 95% confidence interval [CI] 1.09-1.41) and IPI ≥60 months (aRR 1.12, 95% CI 1.00-1.26). In non-IVF deliveries following live birth, risk of PTB was 6.4% for IPI 12 to <24 months (reference); risk of PTB was higher for IPI <12 and ≥60 months (aRR 1.19, 95% CI 1.16-1.21, for both). In both populations, U-shaped or approximately U-shaped associations were observed for SGA and LBW, although the association of IPI <12 months and SGA was not significant in IVF deliveries. In IVF and non-IVF deliveries following nonlive pregnancy outcome, IPI <12 months was not associated with increased risk of PTB, LBW, or SGA, but IPI ≥60 months was associated with significant increased risk of those outcomes in non-IVF deliveries. CONCLUSION(S):Following live births, IPIs <12 or ≥60 months were associated with higher risks of most adverse perinatal outcomes in both IVF and non-IVF deliveries.
| S-EPMC6038145 | biostudies-other
Project description:OBJECTIVE: To determine whether a short interval between pregnancies is an independent risk factor for adverse obstetric outcome. DESIGN: Retrospective cohort study. SETTING: Scotland. SUBJECTS: 89 143 women having second births in 1992-8 who conceived within five years of their first birth. MAIN OUTCOME MEASURES: Intrauterine growth restriction (birth weight less than the 5th centile for gestational age), extremely preterm birth (24-32 weeks), moderately preterm birth (33-36 weeks), and perinatal death. RESULTS: Women whose subsequent interpregnancy interval was less than six months were more likely than other women to have had a first birth complicated by intrauterine growth restriction (odds ratio 1.3, 95% confidence interval 1.1 to 1.5), extremely preterm birth (4.1, 3.2 to 5.3), moderately preterm birth (1.5, 1.3 to 1.7), or perinatal death (24.4, 18.9 to 31.5). They were also shorter, less likely to be married, and more likely to be aged less than 20 years at the time of the second birth, to smoke, and to live in an area of high socioeconomic deprivation. When the outcome of the second birth was analysed in relation to the preceding interpregnancy interval and the analysis confined to women whose first birth was a term live birth (n = 69 055), no significant association occurred (adjusted for age, marital status, height, socioeconomic deprivation, smoking, previous birth weight vigesimal, and previous caesarean delivery) between interpregnancy interval and intrauterine growth restriction or stillbirth. However, a short interpregnancy interval (< 6 months) was an independent risk factor for extremely preterm birth (adjusted odds ratio 2.2, 1.3 to 3.6), moderately preterm birth (1.6, 1.3 to 2.0), and neonatal death unrelated to congenital abnormality (3.6, 1.2 to 10.7). The adjusted attributable fractions for these associations were 6.1%, 3.9%, and 13.8%. The associations were very similar when the analysis was confined to married non-smokers aged 25 and above. CONCLUSIONS: A short interpregnancy interval is an independent risk factor for preterm delivery and neonatal death in the second birth.
| S-EPMC169644 | biostudies-other
Project description:BackgroundCausal interpretation of associations between short interpregnancy interval (the duration from the preceeding birth to the conception of the next-born index child) and the offspring's psychological and educational problems may be influenced by a failure to account for unmeasured confounding.MethodsUsing population-based Swedish data from 1973-2009, we estimated the association between interpregnancy interval and outcomes [autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), severe mental illness, suicide attempt, criminality, substance-use problem and failing grades] while controlling for measured covariates. We then used cousin comparisons, post-birth intervals (the interval between the second- and third-born siblings to predict second-born outcomes) and sibling comparisons to assess the influence of unmeasured confounding. We included an exploratory analysis of long interpregnancy interval.ResultsInterpregnancy intervals of 0-5 and 6-11?months were associated with higher odds of outcomes in cohort analyses. Magnitudes of association were attenuated following adjustment for measured covariates. Associations were eliminated for ADHD, severe mental illness and failing grades, but maintained magnitude for ASD, suicide attempt, criminality and substance-use problem in cousin comparisons. Post-birth interpregnancy interval and sibling comparisons suggested some familial confounding. Associations did not persist across models of long interpregnancy interval.ConclusionsAttenuation of the association in cousin comparisons and comparable post-birth interval associations suggests that familial genetic or environmental confounding accounts for a majority of the association for ADHD, severe mental illness and failing grades. Modest associations appear independently of covariates for ASD, suicide attempt, criminality and substance-use problem. Post-birth analyses and sibling comparisons, however, show some confounding in these associations.
| S-EPMC6124608 | biostudies-literature