Uterine window risk climbs with each prior cesarean, study finds

A retrospective analysis from a large academic maternal-fetal medicine practice suggests that the risk of uterine windows rises substantially with each additional cesarean delivery—and that patients with 3 or more prior cesareans may benefit from delivery before the standard 39-week threshold.

"What we're looking at is something called a uterine window, which is the incomplete separation of a uterine scar from a past C-section," said Xiteng Yan, MD, a maternal-fetal medicine (MFM) fellow at Icahn School of Medicine at Mount Sinai in New York. "Usually, uterine windows are found incidentally during a scheduled C-section. This is a difference from what's called a uterine rupture, which is the complete separation of a uterine scar, and that can be a potentially catastrophic complication for mom and for baby."

The retrospective study included 3295 patients who underwent a planned cesarean between 2005 and 2025. Overall, 216 patients (6.6%) had a uterine window identified at the time of delivery. On regression analysis, having 3 or more prior cesareans was independently associated with uterine windows (adjusted odds ratio [aOR], 3.39; 95% CI, 2.44–4.70), as was a history of prior window or rupture (aOR, 5.38; 95% CI, 3.80–7.63). Notably, unintended labor prior to the scheduled cesarean was not associated with window detection.

The risk escalated markedly with cesarean number. Among patients with no prior history of window or rupture, those with one prior cesarean had approximately a 3% likelihood of a window, rising to 9% with 2 prior cesareans and 15% with 3.

"This is a big jump from the 9% if they have 2 prior C-sections, and the 3% if they just had 1 prior," Yan noted.

Given that labor becomes more likely as pregnancy advances, the investigators argue that earlier delivery should be considered in this population.

"For patients with 3 or more prior C-sections, they may benefit from a slightly earlier delivery, sooner than 39 weeks," Yan said.

The findings raise questions about the current American College of Obstetrics (ACOG) recommendation of 39 weeks for elective repeat cesarean delivery.

"The ACOG recommendation for delivery of elective repeat cesareans is 39 weeks, but unfortunately, it doesn't leave much room for adjustment based on something such as number of prior cesareans," Yan said. "We do think that the ACOG recommendation should be adjusted a little bit to allow for more individualized recommendations for delivery."

For patients with a prior documented window, Yan's practice currently recommends scheduled cesarean delivery between 36 and 38 weeks. Those with a known rupture history are managed per existing guidelines, with delivery at 36 to 37 weeks.

For community OB/GYNs applying these findings outside academic MFM settings, Yan emphasized counseling on warning signs.

"Community providers can definitely take into consideration the increased risk of uterine windows with their higher-order C-sections," Yan said. "It's really worthwhile to counsel their patients to be very cognizant of symptoms concerning for labor, as well as the signs or symptoms of something more concerning, like a uterine rupture."

Any decision about delivery timing, he added, must weigh potential neonatal implications of early-term birth alongside maternal risk.

"Delivery recommendations have to take into consideration a lot of other things, such as the potential impact on the neonate for an early-term delivery, as well as other perinatal outcomes."

Reference:

1. Yan X, Tumfour J, Rebarber A, Bender S, Melka S, Fox NS. The incidence of uterine windows with higher order cesareans: Should we be delivering them earlier? Presented at: Society for Maternal-Fetal Medicine 2026 Pregnancy Meeting. February 8-13, 2026. Las Vegas, Nevada