Abstract
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 IPIs 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, adjOR (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%, adjOR 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 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.
Original language | English |
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Pages (from-to) | 1633-1640 |
Number of pages | 8 |
Journal | BJOG: An International Journal of Obstetrics and Gynaecology |
Volume | 121 |
Issue number | 13 |
DOIs | |
State | Published - Dec 1 2014 |
Bibliographical note
Publisher Copyright:© 2014 Royal College of Obstetricians and Gynaecologists.
Keywords
- Birth spacing
- birth timing
- interpregnancy interval
- preterm birth
ASJC Scopus subject areas
- Obstetrics and Gynecology