Association between long interpregnancy intervals and cesarean delivery due to arrest disorders

It is hypothesized that pregnancy causes time-limited physiologic adaptations of the reproductive system, such as increased blood flow to the uterus. With long interpregnancy intervals, those adaptations may regress, and maternal physiologic characteristics may revert to those of primigravid women. Therefore, it is plausible that long interpregnancy interval is associated with cesarean delivery, especially due to arrest disorders (failed induction of labor, arrest of dilation, or arrest of descent).

To examine the association between interpregnancy interval and cesarean delivery due to arrest disorders in multiparous women without a history of cesarean delivery.

This was a retrospective cohort study of all women who had more than 1 singleton pregnancy at 23 weeks' gestation or greater at MedStar Washington Hospital Center from January 2009 to June 2018. We defined the interpregnancy interval as the duration from the birth of the preceding offspring to the date of conception of the index offspring. We a priori decided to categorize women based on the interpregnancy interval (less than 18 months, 18-59 months, and 60 months or greater). Our primary outcome was cesarean delivery due to arrest disorders. We also examined overall cesarean delivery and cesarean delivery due to nonreassuring fetal heart tracing. Multivariable logistic regression was performed to calculate adjusted odds ratios and 95% confidence intervals, controlling for predefined covariates.

Of 2741 women, 1143 (41.7%), 1369 (49.9%), and 229 (8.4%) had an interpregnancy interval of less than 18 months, 18-59 months, and 60 months or more, respectively. After adjusting for confounders, an interpregnancy interval of 60 months or more compared to an interpregnancy interval of 18-59 months was associated with increased odds of cesarean delivery due to arrest disorders (4.8% vs 1.3%; adjusted odds ratio, 3.06; 95% confidence interval, 1.34-6.97) and cesarean delivery due to arrest of dilation (3.1% vs 0.7%; adjusted odds ratio, 3.24; 95% confidence interval, 1.10-9.59). An interpregnancy interval of less than 18 months compared to an interpregnancy interval of 18-59 months was associated with decreased odds of cesarean delivery due to nonreassuring fetal heart tracing (2.4% vs 4.1%; adjusted odds ratio, 0.55; 95% confidence interval, 0.32-0.92).

An interpregnancy interval of 60 months or greater compared to an interpregnancy interval of 18-59 months was associated with increased odds of cesarean delivery due to arrest disorders. Beneficial effects on postpartum adaptations in the reproductive system may regress as interpregnancy interval increases.