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Influence of interpregnancy interval on birth timing
Author(s) -
DeFranco EA,
Ehrlich S,
Muglia LJ
Publication year - 2014
Publication title -
bjog: an international journal of obstetrics and gynaecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.157
H-Index - 164
eISSN - 1471-0528
pISSN - 1470-0328
DOI - 10.1111/1471-0528.12891
Subject(s) - medicine , gestational age , gestation , population , obstetrics , odds ratio , birth weight , live birth , cohort , pregnancy , pediatrics , biology , genetics , environmental health
Objective To assess the influence of inadequate birth spacing on birth timing distribution across gestation. Design Population‐based retrospective cohort study using vital statistics birth records. Setting Ohio, USA . Study Population Singleton, non‐anomalous live births ≥20 weeks to multiparous mothers, 2006–2011. Methods Birth frequency at each gestational week was compared following short IPI s of <6, 6–12 and 12–18 months versus referent group, normal IPI ≥18 months. Main outcome measures Frequency of birth at each gestational week; preterm <37 weeks; <39 and ≥40 weeks. Results 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, adj 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 , P < 0.001. Likewise, birth at ≥40 weeks was decreased (16.9%) following short IPI <12 months compared to normal IPI , 23.2%, adj 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. Conclusions 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 IPI s 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.