Effect of interpregnancy interval on preterm birth risk after 14 to 34 week delivery

Data show definite risks of interpregnancy intervals < 6 months after full-term delivery, and no benefit of waiting to conceive after a first-trimester miscarriage. It is unclear which advice to give after early preterm delivery. We compared the influence of interpregnancy interval on the subsequent delivery in women whose index pregnancy ended 14-34 weeks versus those that delivered after 34 weeks. We performed a retrospective cohort study of all deliveries 14 and 34 weeks that have a subsequent delivery on our labor floor between 1/1/2001 and 9/30/2017. We examined the relationship between interpregnancy interval and gestational age of the subsequent pregnancy. We separated the initial deliveries into 14-28 weeks and 28-34 weeks to highlight any differences between the second and third-trimester deliveries. Out of a total of 11,107 delivery pairs, 543 had an initial delivery 14-34 weeks and 10,564 were > 34 weeks. The gestational age at delivery of the subsequent pregnancy did not vary by the interpregnancy interval (Figure 1). We compared the percent of pre-viable (< 22 weeks), peri-viable (22-26 weeks), early pre-term (26-34 weeks) and late pre-term (34-37 weeks) births within categories of interpregnancy intervals. The rate of pre-term birth categories did not differ significantly by interpregnancy interval category (Figure 2). Overall, there is no benefit of waiting to conceive after delivering between 14 and 34 weeks. Future studies should incorporate procedures outside of labor and delivery to capture other pregnancy outcomes.View Large Image Figure ViewerDownload Hi-res image Download (PPT)