Influence of interpregnancy interval on birth timing. (4th June 2014)

• Record Type: Journal Article
• Authors: DeFranco, EA; Ehrlich, S; Muglia, LJ
• Is Part Of: BJOG. Volume 121:Number 13(2014)
• Page Start: 1633
• Page End: 1640
• Publication Date: 2014-06-04
• Subjects: Obstetrics -- Periodicals; Gynecology -- Periodicals; 618
• DOI: 10.1111/1471-0528.12891
• Languages: English
• ISSNs: 1470-0328

Abstract

<abstract abstract-type="main" id="bjo12891-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="bjo12891-sec-0001" sec-type="section"> <title>Objective</title> <p>To assess the influence of inadequate birth spacing on birth timing distribution across gestation.</p> </sec> <sec id="bjo12891-sec-0002" sec-type="section"> <title>Design</title> <p>Population‐based retrospective cohort study using vital statistics birth records.</p> </sec> <sec id="bjo12891-sec-0003" sec-type="section"> <title>Setting</title> <p>Ohio, USA.</p> </sec> <sec id="bjo12891-sec-0004" sec-type="section"> <title>Study Population</title> <p>Singleton, non‐anomalous live births ≥20 weeks to multiparous mothers, 2006–2011.</p> </sec> <sec id="bjo12891-sec-0005" sec-type="section"> <title>Methods</title> <p>Birth frequency at each gestational week was compared following short IPIs of <6, 6–12 and 12–18 months versus referent group, normal IPI ≥18 months.</p> </sec> <sec id="bjo12891-sec-0006" sec-type="section"> <title>Main outcome measures</title> <p>Frequency of birth at each gestational week; preterm <37 weeks; <39 and ≥40 weeks.</p> </sec> <sec id="bjo12891-sec-0007" sec-type="section"> <title>Results</title> <p>Of 454 716 births, 87% followed a normal IPI ≥18 months, 10.7% had IPI 12–18 months and 2.2% with IPI <12 months. The risk of delivery <39 weeks was higher following short IPI <12 months, <sub>adj</sub>OR (odds ratio) 2.78 (95% CI 2.64, 2.93). 53.3% of women delivered before the 39th week after IPI <12 months compared with 37.5% of women with normal IPI, <italic> P </italic>< 0.001. Likewise, birth at ≥40 weeks was decreased (16.9%) following short IPI <12 months compared to normal IPI, 23.2%, <sub>adj</sub>OR 0.67 (95% CI 0.64, 0.71). This resulted in a shift of the frequency distribution curve of birth by week of gestation to the left for pregnancies following a short IPI <12 months and 12–18 months compared to, birth spacing ≥18 months.</p> </sec> <sec id="bjo12891-sec-0008" sec-type="section"> <title>Conclusions</title> <p>While short IPI is a known risk factor for preterm birth, our data show that inadequate birth spacing is associated with decreased gestational age for all births. Pregnancies following short IPIs have a higher frequency of birth at all weeks of gestation prior to 39 and fewer births ≥40 weeks, resulting in overall shortened pregnancy duration.</p> </sec> </abstract>