Predictors of successful external cephalic version and assessment of success for vaginal delivery.

OBJECTIVE: To identify predictors of successful external cephalic version (ECV) and to compare delivery outcome between women who had a successful ECV and women with spontaneous vertex presentation.

METHODS: A retrospective cohort study of all women who underwent ECV in a single tertiary medical center between 2007 and 2011. Delivery outcome was compared between women who underwent a trial of vaginal delivery following successful ECV with that of a control group in a 2:1 ratio. Multivariate analysis was used to identify predictors of successful ECV.

RESULTS: Overall 287 were eligible for the study group. Of these 130 (45.3%) had a successful ECV. Polyhydramnios was the strongest factor associated with successful ECV (OR=3.1, 95%-CI 1.4-7.2), followed by transverse lie (versus breech presentation, OR=2.6, 95%-CI 1.2-6.7) and a posterior placenta (OR=1.7, 95%-CI 1.1-3.9), while nulliparity was associated with a lower likelihood of successful ECV (OR=0.4, 95%-CI 0.2-0.6). Women who had a successful ECV and underwent a trial of labor were more likely to deliver by operative vaginal delivery (OVD) (OR=1.8, 95%-CI 1.2-3.6), mainly due to a higher rate of prolonged 2nd, but were not at an increased risk for CS (OR=0.9, 95%-CI 0.4-2.4).

CONCLUSIONS: Counselling to women prior to ECV should address the likelihood of success based on the predicting factors described above, as well as the increased risk for OVD in the case of successful ECV.