Full dilation cesarean section: a risk factor for recurrent second-trimester loss and preterm birth

A previous cesarean section at full dilation (FDCS) is a risk factor for preterm birth. To provide insight into the risk to subsequent pregnancies, this cohort study compares the outcomes of pregnant women with a previous preterm birth associated with either a prior FDCS or a prior term vaginal delivery.

We identified women attending two inner-city preterm surveillance clinics (Guy's and St Thomas Hospital and University College London Hospital, London, UK) who had a spontaneous late miscarriage (14⁺⁰ -23⁺⁶ weeks) or spontaneous preterm birth (sPTB; <37 weeks' gestation) following a term pregnancy, and then a further pregnancy for analysis. Cases were those with a prior term FDCS, whereas controls had a prior term vaginal birth; both before the late miscarriage/sPTB. Main outcomes were gestational age at delivery and delivery at <30 weeks in the next (third) pregnancy.

Over the study period, 66 women were identified who had a term delivery followed by a late miscarriage or sPTB, and a subsequent pregnancy. Recurrent sPTB <30 weeks was more common in cases than in controls (12/29, vs. 5/37, p = 0.02, Fisher's exact test, RR 3.06, 95% CI 1.22-7.71). Median gestation at delivery was significantly lower [249 days (IQR 154, 267) vs. 280 days (IQR 259, 280) p < 0.001]. Eleven women in the FDCS group received vaginal cerclage, five of whom delivered <37 weeks.

In this cohort study we observed that women with a term FDCS and subsequent late miscarriage/sPTB have a higher risk of recurrent sPTB compared with women whose first term delivery was vaginal.