Mode of delivery and subsequent fertility.

STUDY QUESTION: When compared with vaginal delivery, is Cesarean delivery associated with reduced childbearing, a prolonged inter-birth interval or infertility? SUMMARY ANSWER: Women whose first delivery was by Cesarean section were not significantly different from those who delivered vaginally with respect to subsequent deliveries, inter-birth interval or infertility after delivery. WHAT IS ALREADY KNOWN: Some studies have suggested that delivery by Cesarean section reduces subsequent fertility, while others have reported no association. STUDY DESIGN, SIZE, DURATION: This was a planned secondary analysis of the Mothers' Outcomes After Delivery study, a longitudinal cohort study. This analysis included 956 women with 1835 deliveries, who completed a study questionnaire at 6-11 years (median [interquartile range]: 8.1 [7.1, 9.8]) after their first delivery. PARTICIPANTS/MATERIALS, SETTING,
METHODS: Exclusion criteria regarding the first birth were: maternal age <15 or >50 years, delivery at <37 weeks gestation, placenta previa, multiple gestation, known fetal congenital abnormality, stillbirth, prior myomectomy and abruption. Of the 956 women included, the first delivery was by Cesarean section for 534 women and by vaginal birth for 422 women. Infertility was self-reported. To compare maternal characteristics by mode of first delivery, P-values were calculated using Fisher's exact test or Pearson's χ(2) test for categorical variables and a Kruskall-Wallis test for continuous variables. We also considered whether, across all deliveries to date, a prior Cesarean is associated with decreased fertility. In this analysis, self-reported infertility after each delivery (across all participants) was considered as a function of one or more prior Cesarean births, using generalized estimating equations to control for within-woman correlation. MAIN RESULTS AND THE ROLE OF CHANCE: No differences were observed between the Cesarean and vaginal groups (for first delivery) with respect to infertility after their most recent delivery (7 versus 6%, P = 0.597), the interval between their first and second births (30.8 versus 30.6 months, P = 0.872), or multiparity (75 versus 76%, P = 0.650). Across all births, a history of Cesarean delivery was not significantly associated with infertility (odds ratio [OR], 0.90; 95% confidence interval [CI], 0.64-1.26). Women who reported infertility prior to their first delivery were significantly more likely to report infertility after each subsequent delivery (OR, 5.16; 95% CI, 3.60-7.39). LIMITATIONS, REASONS FOR CAUTION: Due to the use of self-reported infertility, the fertility status of some participants may be misclassified. Also, the small sample size may result in insufficient power to detect small differences between groups. Finally, a relatively high proportion of our participants were over age 35 at the time of first delivery (26%) and highly educated (37% with graduate degrees), which may indicate that our population may not be generalizable. WIDER IMPLICATIONS OF THE
FINDINGS: While some prior studies have shown decreased family size among women who deliver by Cesarean, our results suggest that the rate of infertility is not different after Cesarean compared with vaginal birth. Our findings should be reassuring to women who deliver by Cesarean section. STUDY FUNDING/COMPETING INTERESTS: This study was funded by the US National Institutes of Health (NIH, R01-HD056275). No competing interests are declared. TRIAL REGISTRATION NUMBER: N/A.