The risk of placenta accreta following primary cesarean delivery

To (a) evaluate the risk for placenta accreta following primary cesarean section (CS), in regard to the stage of labor, the cesarean section was taken (elective prelabor vs. unplanned during labor); and (b) investigate whether the association between placenta accreta and maternal and neonatal complications is modified by the type of the primary CS.

In a population-based retrospective cohort study, we included all singleton deliveries occurred in Soroka University Medical Center between 1991 and 2015, of women who had a history of a single CS. The deliveries were divided into three groups according to the delivery stage the primary CS was carried out: 'Unplanned 1' (first stage-up to 10 cm), 'Unplanned 2' (second stage-10 cm) and 'Elective' prelabor CS. We assessed the association between the study group and placenta accreta using logistic generalized estimation equation (GEE) models. We additionally assessed maternal and neonatal complications associated with placenta accreta among women who had elective and unplanned CS separately.

We included 22,036 deliveries to 13,727 women with a history of one CS, of which 0.9% (n = 207) had placenta accreta in the following pregnancies: 12% (n = 25) in the 'Unplanned 1' group, 7.2% (n = 15) in the ' Unplanned 2' group and 80.8% (n = 167) in the 'elective' group. We found no difference in the risk for subsequent placenta accreta between the groups. In a stratified analysis by the timing of the primary cesarean delivery, the risk for maternal complications, associated with placenta accreta, was more pronounced among women who had an unplanned CS (OR 27.96, P < 0.01) compared to women who had an elective cesarean delivery (OR 13.72, P < 0.01).

The stage in which CS is performed has no influence on the risk for placenta accreta in the following pregnancies, women who had an unplanned CS are in a higher risk for placenta accrete-associated maternal complications. This should be taken into consideration while counselling women about their risk while considering trial of labor after cesarean section.