[Usefulness of ultrasound measurement of the lower uterine segment before delivery of women with a prior cesarean: literature review].

Identifying women with a history of cesarean delivery and at real risk for uterine rupture is an important aim in obstetric care. It is with this objective that different authors have evaluated the interest of ultrasound for predicting the risk of a cesarean scar defect by measuring the thickness of the lower uterine segment. The literature is sparse and subject to numerous biases because they are mainly prospective cohort studies with small numbers. However, the results are concordant: Ultrasound measurements of lower uterine segment thickness are strongly correlated with the operative findings observed during cesarean delivery. Moreover, the thinner the lower uterine segment on ultrasound, the higher the likelihood of a uterine defect. Two randomized trials have recently been published. The PRISMA cluster randomized controlled trial evaluated a multifaceted intervention including an ultrasound estimation of the risk of uterine rupture by ultrasound measurement of the lower uterine segment thickness and aimed at helping women in their choice of mode of delivery after a previous cesarean delivery. This multifaceted intervention resulted in a significant reduction in the rates of major perinatal and maternal morbidity, without any increase in the rate of cesarean delivery or uterine rupture. However, due to its design, it is impossible to specifically specify the benefit of lower uterine segment measurement in reducing major maternal and perinatal morbidity since the trial combined several interventions. The LUSTrial randomized controlled trial evaluated the impact on maternal-fetal morbidity and mortality of proposing a mode of delivery based on ultrasound measurement of the lower uterine segment thickness compared to usual care among women with a history of cesarean delivery. Ultrasound measurement of lower uterine segment thickness was not associated with a statistically significant reduction in maternal-fetal morbidity and mortality compared to usual care. In this literature review, we will mainly detail and analyze the results of this trial.