Background Spontaneous miscarriage (the death of a fetus before 20 weeks of pregnancy), occurs in 10–15% of recognised pregnancies. Stillbirth (the death of a fetus after 24 weeks of pregnancy), occurs in approximately one in every 200 deliveries. The cause of miscarriage and stillbirth is frequently unknown. However, there is some evidence to suggest that previous Caesarean delivery may be a risk factor.
Objective: to compare the risk of fetal death in subsequent pregnancy by mode of delivery.
Methods This was a systematic review of relevant studies identified through CINAHL, the Cochrane library, Embase, Medline, PubMed, SCOPUS and Web of Knowledge (1945 - November 2011), using a comprehensive search strategy, and cross-checking of reference lists. Study selection: cohort and case-control studies reporting on Caesarean delivery and spontaneous miscarriage or stillbirth. Two reviewers independently assessed titles, abstracts, and full articles to identify eligible studies, using a standardised data collection form.
Results Miscarriage: From 6,857 titles identified, eight articles were included, totalling 147,017 women and 12,682 events. Odds ratios (ORs) were combined using a fixed-effect model to estimate the overall association using Review Manager Software. From the meta-analysis, the pooled OR estimate of miscarriage among women who previously delivered by Caesarean versus vaginally, was 1.11 [95% CI 1.06,1.17]. The OR of miscarriage was 1.26 [95% CI 0.54,2.92] for one case-control study, 1.11 [95% CI 1.06,1.17] for seven cohort studies and 1.11 [95% CI 1.06,1.17] for primiparous women (eight studies).
Stillbirth: From 6,857 studies identified, seven articles were included, totalling 1,661,335 pregnancies and 5,741 events. ORs were combined using a random effect model (due to the heterogeneity of included studies) to estimate the overall association. From the meta-analysis, the pooled OR estimate of stillbirth among women who previously delivered by Caesarean versus vaginally, was 1.32 [95% CI 1.11,1.57]. The OR of stillbirth was 1.30 [95% CI 1.03,1.64] for primiparous women (five studies), 1.40 [95% CI 1.24,1.59] for multiparous women (two studies), 1.80 [95% CI 1.27,2.55] for studies including all stillbirths (five studies) and, 1.20 [95% CI 1.02,1.42] for studies including only unexplained antepartum stillbirths (three studies).
Conclusion Caesarean delivery compared to vaginal delivery is associated with an increased risk of spontaneous miscarriage by 11% and stillbirth by 32% in subsequent pregnancies. In light of the recently published National Institute for Health and Clinical Excellence (NICE) guidelines, which support a woman’s right to request a Caesarean delivery without medical reason, there is an urgent need to establish whether mode of delivery has a causal effect on risk of fetal death.
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