Obstetric factors for unsuccessful trial of labor in second-order birth following previous cesarean

The trial of labor after previous cesarean (TOLAC) is an important strategy to limit repeat cesarean sections and their complications. An unsuccessful TOLAC leads to maternal and neonatal morbidities. The success or failure of TOLAC after the first cesarean is determinant for the subsequent vaginal birth. Limited studies are available from low-income countries, exclusively conducted in women in their sec.ond-order birth following the first cesarean section. This study aims at determining the frequency of unsuccessful attempts at vaginal delivery in the second-order term (37-41+6/7 weeks) birth among women with previous cesarean sections and to describe maternal and obstetric factors for unsuccessful laborTOLACs in the same group.

A cross-sectional study conducted from April to December 2010 at Obstetrics & Gynaecology Unit II, Civil Hospital Karachi.

All eligible patients at term pregnancy in their second-order birth were included. The frequency of unsuccessful attempts at vaginal birth was determined, followed by secondary analysis by calculating odds ratio for maternal and obstetric factors, that is, body mass index (BMI), hight, gestation ≥40 weeks, interdelivery interval, engagement of head in 5th, estimated fetal weight, ruptured membranes, duration of labor ≥7 hours, augmentation of labor, cervical dilatation < 4 cm, and vertex station -2 or higher on admission.

Out of 122 study subjects, the proportion of unsuccessful vaginal birth after cesarean (VBAC) was 27.9% (n=34). Among maternal and obstetric factors, BMI > 25 (AOR, 5.00), gestation ≥40 weeks (AOR, 5.45), cervical dilatation < 4 cm (AOR, 5.90), and station of vertex -2 or higher (AOR, 3.83) had highly significant adjusted odds for failed TOLAC.

With a well-defined protocol, the rates of unsuccessful attempts at VBAC are not high for the second-order birth. The risk of failure can be anticipated by factors such as BMI > 25, pregnancy duration ≥40 weeks, cervical dilatation < 4 cm, and vertex station -2 or higher on admission.