Primary mode of delivery and subsequent pregnancy

OBJECTIVE: To investigate the relationship between primary mode of delivery and subsequent pregnancy and to compare the findings with a previous study conducted on an earlier cohort from the same population. DESIGN: Population cohort. SETTING: Aberdeen City, Scotland. POPULATION: Women who delivered their first singleton child in Aberdeen Maternity Hospital between 1980 and 1997. METHODS: Population-based data relating to the index and next pregnancy event, if any, were obtained from the Aberdeen Maternity Neonatal Databank. Subsequent pregnancy was compared across the three modes of delivery groups using log rank tests and Cox proportional hazards regression models. MAIN OUTCOME MEASURE: First subsequent pregnancy following index delivery. RESULTS: Women who delivered by caesarean section (CS) were less likely to have a subsequent pregnancy compared with those who had a spontaneous vaginal delivery (SVD), hazard ratio = 0.91 (95% CI 0.87, 0.95). This confirmed the findings of a previous study conducted on an earlier cohort of the same population. The median time to next pregnancy following CS was 36.3 months, 31.8 months following instrumental vaginal delivery (IVD) and 30.4 months following SVD. In contrast to the earlier study where women who had an instrumental delivery were found to be an intermediate group, we found no difference in subsequent pregnancy following IVD compared with SVD, HR = 1.0 (95% CI 0.96, 1.03). CONCLUSIONS: Following an initial delivery by CS, fewer women went on to have another pregnancy compared with SVD. The incidence of subsequent pregnancy is similar following instrumental and SVD.