In recent decades, the rate of cesarean section delivery has steadily increased worldwide ranging at 30% of deliveries, thus long-term risks after cesarean section need to be evaluated. Postoperative risks include, among others, uterine scar rupture and placental complications such as placenta previa and accreta- complications, which are possibly associated with uterine scar dehiscence.

The prevalence of lower-segment uterine scar deficiency has previously been described as 63%. One recent systematic review and meta analysis investigated closure techniques of low transverse cesarean. No significant difference in risk of uterine scar defect comparing single layer versus double layer closure could be detected (RR 0.53), whereas in women with single layer closure, a lower residual myo-metrial thickness was observed (-2.6mm). However, the authors do conclude that data is insufficient to determine the risk of uterine rupture, dehiscence or gynecological outcomes due to insufficient power of available studies. A recently published Randomized Controlled Trial concluded that double-layer closure with unlocked first layer showed a better scar healing than locked single layer.

The investigators main objective is to identify if single-layer suture of the uterus during cesarean section results in a higher rate of cesarean scar deficiency than double-layer suture.

Interventions

Single- layer versus double- layer uterine closure Two different techniques of uterine closure in cesarean section will be compared: single- layer versus double- layer continuous uterotomy suture.

Standardized transvaginal sonography

Transvaginal ultrasound examination is carried out by one expert sonographer. The ultrasound machine used for all examinations is GE Voluson E10.

Primary outcome: CS scar deficiency visualized in transvaginal ultrasound at 3 months after CS (yes/no).

Secondary outcome: Myometrial thickness at the site of uterine scar (mm).

Inclusion Criteria:

• First cesarean section
• Scheduled cesarean section at Department of Obstetrics and Gynecology, Medical University of Vienna
• Age ≥ 18 years
• Informed Consent
• Cesarean section at ≥ 37+0 weeks of gestation

Exclusion Criteria:

• Previous cesarean section
• Emergency cesarean section
• Cesarean section < 37+0 weeks of gestation
• Corporal incision during cesarean section
• Diseases which favor wound healing disruptions (e.g. chronic inflammatory diseases)
• Uterine anatomic anomalies
• BMI > 35kg/m2
• Placenta previa