(394) The Incidence of Uterine Windows with Higher Order Cesareans: Should We Be Delivering Them Earlier?

A uterine dehiscence or window refers to the clinically occult separation of a uterine scar. This study’s objective was to determine risk factors for windows and the likelihood of windows based on number of prior cesareans.

Study Design:
This was a retrospective study of patients who underwent a planned Cesarean in a single, large, academic, MFM practice from 2005 to 2025. We excluded patients who attempted labor or trial of labor after Cesarean. We compared patients with and without a uterine window at delivery.  Characteristics of interest include total prior Cesareans, prior window or rupture, and whether labor occurred prior to scheduled delivery. We also evaluated the likelihood of a window based on number of total prior cesareans. Bivariate analysis was performed using T-tests, Mann Whitney-U tests and chi-square tests.

Results:

A total of 3295 patients were included- 216 (6.6 %) patients had windows, 3079 (93.4%) did not. Clinical features associated with windows are in Table 1.  Unintended labor prior to cesarean was not associated with finding a window. On regression analysis, factors associated with a window were having three or more prior Cesareans (aOR 3.39, 95% CI 2.44-4.7) and a history of window or rupture (aOR 5.38, 95% CI 3.8-7.63). The frequency of dehiscence increased with each number of Cesarean (Table 2). Amongst patients without a prior window or rupture, the likelihood of finding a window was 0.3% at the first cesarean, 2.7% at second cesarean, 8.7% at third cesarean, 15.3% at fourth cesarean, 9.5% at fifth cesarean, and 19.1% at the sixth or higher cesarean (p < 0.001).

Conclusion:

There is an approximately 1-in-10 risk of uterine window in patients with three or more prior Cesareans. This risk increases further with the number of prior Cesareans. Because these patients are at high risk for dehiscence, even if delivered before the onset of labor or had no prior history of dehiscence, delivery should be considered in the early term period (i.e., before ACOG’s recommendation for elective delivery at 39 weeks).