Journal article
Re-evaluation of link between interpregnancy interval and adverse birth outcomes: retrospective cohort study matching two intervals per mother
BMJ (Online), Vol.349(jul23 1), pp.g4333-g4333
2014
PMCID: PMC4137882
PMID: 25056260
Abstract
To 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.
Retrospective 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.
Perth, Western Australia, 1980-2010.
40 441 mothers who each delivered three liveborn singleton neonates.
Preterm birth (<37 weeks), small for gestational age birth (<10th centile of birth weight by sex and gestational age), and low birth weight (<2500 g).
Within 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.
This 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.
Details
- Title
- Re-evaluation of link between interpregnancy interval and adverse birth outcomes: retrospective cohort study matching two intervals per mother
- Authors/Creators
- Stephen J Ball - The Kids Research Institute AustraliaGavin Pereira - The Kids Research Institute AustraliaPeter Jacoby - The Kids Research Institute AustraliaNicholas de Klerk - The Kids Research Institute AustraliaFiona J Stanley - The Kids Research Institute Australia
- Publication Details
- BMJ (Online), Vol.349(jul23 1), pp.g4333-g4333
- Publisher
- BMJ Publishing Group Ltd
- Identifiers
- 991005571142407891
- Copyright
- © 2014 BMJ Publishing Group Ltd
- Murdoch Affiliation
- Ngangk Yira Institute for Change
- Language
- English
- Resource Type
- Journal article
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- 1.72 Obstetrics & Gynecology
- 1.72.182 Maternal-Fetal Health
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