Preoperative ultrasound assessment for surgical risk management in patients with a placenta previa and a history of cesarean delivery

Patients with a history of 2 or more cesarean deliveries who present with placenta previa are at high risk for complex cesarean delivery (level III) and should be evaluated and managed by an expert multidisciplinary team. Preoperative ultrasound examinations can accurately identify signs associated with abnormalities of the uteroplacental interface, uterine contour, and uteroplacental vascularity. Key ultrasound markers of uterine remodeling following cesarean deliveries, such as myometrial thinning associated with placental bulging, can inform the surgical team about the potential for complex dissection of the lower uterine segment and the risk of bladder injury. These markers can also help identify patients with a major dehiscence who may require a cesarean hysterectomy due to the inability to effectively reapproximate the hysterotomy edges and repair the lower uterine segment. When these markers are associated with subplacental hypervascularization and the presence of intraplacental lacunae, there is a high probability of placenta accreta spectrum, which increases the risk of major intraoperative bleeding. Ultrasound signs associated with pelvic adhesions remain challenging to evaluate preoperatively, necessitating further investigations. A standardized protocol for obtaining preoperative images in patients at high risk for complex cesarean delivery should include detailed assessments of the placental position, size of uterine dehiscence, evidence and location of the placental bulge, and color Doppler mapping of uteroplacental, intraplacental, and bladder interface circulations, as well as cervical changes, using both transabdominal and transvaginal scans. Such a protocol would facilitate effective surgical risk management and counseling and could be beneficial for remote preoperative teleconsultation.