Influence of interpregnancy interval on birth timing

E. A. DeFranco, S. Ehrlich, L. J. Muglia

Research output: Contribution to journalArticlepeer-review

41 Scopus citations


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 languageEnglish
Pages (from-to)1633-1640
Number of pages8
JournalBJOG: An International Journal of Obstetrics and Gynaecology
Issue number13
StatePublished - Dec 1 2014

Bibliographical note

Publisher Copyright:
© 2014 Royal College of Obstetricians and Gynaecologists.


  • Birth spacing
  • birth timing
  • interpregnancy interval
  • preterm birth

ASJC Scopus subject areas

  • Obstetrics and Gynecology


Dive into the research topics of 'Influence of interpregnancy interval on birth timing'. Together they form a unique fingerprint.

Cite this