Third trimester assessment of the uterine scar in women with prior caesarean: what is the evidence?

The increasing rate of caesarean delivery is a worldwide concern. A major contributor to this evolution has been a concomitantly decline in vaginal birth after caesarean, because of the risk of intrapartum uterine rupture, which is a rare but potentially catastrophic complication of a trial of labour after caesarean (TOLAC). On the other hand, elective repeat caesarean is associated with surgical complications and risk of abnormal placentation (e.g. placenta accreta) in subsequent pregnancies. Therefore TOLAC is recommended to women with good prognosis of success and low risk of uterine rupture. The published data suggest that sonographic assessment of lower uterine segment in third trimester could potentially play an important role in the prediction of uterine rupture in women with previous caesarean.