Caesarean delivery and subsequent pregnancy interval: a systematic review and meta-analysis

Background: Caesarean delivery has increased worldwide, however, the effects on fertility are largely unknown. This systematic review aims to compare subsequent sub-fertility (time to next pregnancy or birth) among women with a Caesarean delivery to women with a vaginal delivery. Methods: Systematic review of the literature including seven databases: CINAHL; the Cochrane Library; Embase; Medline; PubMed; SCOPUS and Web of Knowledge (1945 -October 2012), using detailed search-strategies and reference list cross-checking. Cohort, case-control and cross-sectional studies were included. Two assessors reviewed titles, abstracts, and full articles using standardised data abstraction forms and assessed study quality. Results: 11 articles were eligible for inclusion in the systematic review, of these five articles which adjusted for confounders were combined in a meta-analysis, totalling 750,407 women using fixed-effect models. Previous Caesarean delivery was associated with an increased risk of sub-fertility [pooled odds ratio (OR) 0.90; 95% CI 0.86, 0.93]. Subgroup analyses by parity [primiparous women: OR 0.91; 95% CI 0.87, 0.96; not limited to primiparous women: OR 0.81; 95% CI 0.73, 0.90]; by publication date (pre-2000: OR 0.80, 95% CI 0.68, 0.94; post-2000: OR 0.90, 95% CI 0.86, 0.94); by length of follow-up (< 10 years: OR 0.81, 95% CI 0.73, 0.90; > 10 years: OR 0.91, 95% CI 0.87, 0.96); by indication for mode of delivery (specified: 0.92, 95% CI 0.88, 0.97; not specified: OR 0.81, 95% CI 0.73, 0.90); by cohort size (< 35,000: OR 0.79, 95% CI 0.67, 0.92; > 35,000: OR 0.90, 95% CI 0.87, 0.95), by definition of sub-fertility used divided into (birth interval [BI]: OR 0.89, 95% CI 0.84, 0.94; inter-pregnancy interval [IPI]: OR 0.91, 95% CI 0.85, 0.97; and categorical measures: OR 0.81, 95% CI 0.73, 0.90); continuous measures: OR 0.91, 95% CI 0.87, 0.96) were performed. Results of the six studies not included in the meta-analysis (which did not adjust for confounders) are presented individually. Conclusions: The meta-analysis shows an increased waiting time to next pregnancy and risk of sub-fertility among women with a previous Caesarean delivery. However, included studies are limited by poor epidemiological methods such as variations in the definition of time to next pregnancy, lack of confounding adjustment, or details of the indication for Caesarean delivery. Further research of a more robust methodological quality to better explore any underlying causes of sub-fertility and maternal intent to delay childbearing is warranted.