The goal of this trial is to examine if the completion or omission of a bladder flap impacts the location and formation of cesarean scar niche in women undergoing primary cesarean section. The main question it aims to answer is if omission of a bladder flap changes the prevalence of cesarean scar niche on a 6-8 week postpartum ultrasound. Researchers will compare participants that have a bladder flap made to those that have a bladder flap omitted at time of their primary cesarean delivery. Participants will have routine postpartum care and be asked to return for a 6-8 week postpartum transvaginal ultrasound.

As the rate of cesarean deliveries increases globally, the importance of a cesarean scar niche (CSN) has evolved into a significant clinical concern with long term obstetric and gynecologic implications including increasing risk for placenta accreta spectrum (PAS) in future pregnancies and abnormal uterine bleeding. In fact, the main cause of PAS is placentation into uterine scars secondary to cesarean deliveries

Bladder flap formation is a standard step in cesarean deliveries and involves dissecting the bladder off the uterus to push it inferiorly to allow better access to the lower uterine segment for hysterotomy and decrease risk of bladder injury. The lower uterine segment is targeted for hysterotomy as it has been shown that the proportion of muscle tissue and the thickness of the wall of the uterus increases as one travels from the cervix to the fundus. Therefore, by making an incision in the lower uterine segment, the surgeon has less tissue to go through to deliver the fetus and disrupts less muscle to preserve uterine myometrial integrity. While studies have suggested bladder flap omission in primary cesarean deliveries does not increase intraoperative complications and reduces operating time. CSN assessment was not an outcome evaluated in these studies and the decision to omit or perform a bladder flap is at the discretion of the surgeon.

Previous studies have looked at different surgical techniques and different cervical dilations at time of cesarean delivery and the impact on niche formation and location. There has been no consensus on hysterotomy or other surgical techniques to decrease risk of CSN formation. To our knowledge, there have not been studies that have assessed postoperative CSN in relation to completion or omission of a bladder flap prior to hysterotomy. As such, the investigator team hypothesizes that omission of a bladder flap lends itself to a more cephalad hysterotomy and potentially more clinically significant CSNs.

Inclusion Criteria:

• Age 18 years or older
• Primary low transverse cesarean section performed at Montefiore Weiler or Wakefield Hospitals
• Able to provide informed consent in English or Spanish
• Plan for postpartum care at Montefiore Medical Center

Exclusion Criteria:

• History of a prior uterine surgery
• Known congenital uterine anomalies
• Inability to safely access lower uterine segment at time of delivery
• Hysterotomy is extended past/outside the lower uterine segment at time of surgery
• Hysterectomy is indicated prior to postpartum follow-up

De-identified individual participant data (IPD) that underlie the results reported in future publications will be made available to qualified researchers upon request

Beginning 6 months after trial publication for a period of up to 5 years.

Requests will require a data use agreement and a proposal review by the study team.