Dataset Information

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

ABSTRACT:

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.

SUBMITTER: Congdon JL

PROVIDER: S-EPMC9023393 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

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Publications

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

Congdon Jayme L JL Baer Rebecca J RJ Arcara Jennet J Feuer Sky K SK Gómez Anu Manchikanti AM Karasek Deborah D Oltman Scott P SP Pantell Matthew S MS Ryckman Kelli K Jelliffe-Pawlowski Laura L

Maternal and child health journal 20220309 5

<h4>Introduction</h4>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.<h4>Methods</h4>For this retrospective cohort study, data were drawn from a California De ...[more]

PMID: 35260953

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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.

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.

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.

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.

Dataset Information

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

Introduction

Methods

Results

Discussion

Publications

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

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