Preoperative and Intraoperative Sonographic Assessment of Lower Uterine Segment Thickness at Term in Women With Previous Cesarean Delivery - a Ultrasound Method Comparison Study

In 1991, 126.297 (15.3%) women delivered by caesarean section in Germany. Since then, the rate of caesarean section increased steadily over the next 20 years, reaching up to 32.2% in 2011 \[https://www.destatis.de\]. The absolute risk of uterine rupture in vaginal birth after Caesarean section is 1 in 100 deliveries. The risk of perinatal death or the outcome of extremely neurological impairment is 1 in 1000 deliveries \[Cunningham et al., 2009\]. Statistically more than 300 pregnant women with a prior caesarean delivery visit daily ultrasound departments of german hospitals to investigate the C-section scar before delivery. They have one important question: Is it possible to predict successful trial of labor after cesarean delivery? \[AQUA-Institut\] The information for the risk of uterine rupture remains insufficient based only on ultrasonography assessment \[Varner et al., 2012\]. The measurement technique for lower uterine segment (myometrial) thicknesses in the third trimester have been described by several authors. Using a combination of preoperative transvaginal and transabdominal (linear/convex probe) ultrasound, we compare with intraoperative sonographic assessment of lower uterine segment of women who underwent ≥ second cesarean section. The aim of the present study is to assess transabdominal (linear/convex ultrasound probe) and transvaginal approach versus intraoperative sonographic assessment of lower uterine segment. This will allow the investigators to draw conclusions regarding the best method to assessment of lower uterine segment (myometrial) thickness in the third trimester to predict successful trial of labor after cesarean delivery.