Spontaneous preterm birth following unintended hysterotomy extension during second-stage labor cesarean delivery

Unintended hysterotomy extensions occur frequently during second-stage cesarean delivery and may result in uterine and cervical tissue trauma. The impact of these extensions on adverse outcomes in subsequent pregnancies, including spontaneous preterm birth (sPTB), remains unknown.

We evaluated the association between unintended hysterotomy extension during second-stage cesarean delivery and subsequent sPTB.

This was a retrospective cohort study of patients who underwent a primary cesarean delivery during the second stage of labor between March 2014 and August 2024 and had a subsequent delivery ≥14 weeks at a single academic tertiary care center in the Southeastern United States. Unintended hysterotomy extension was defined as any documented extension beyond the initial hysterotomy as recorded in the operative notes of the electronic health record. Patients who underwent cesareans with intentionally inverted T or J incisions were excluded. The primary outcome was the occurrence of sPTB (delivery <37 0/7 weeks' gestation) in the subsequent pregnancy. Secondary outcomes included subsequent pregnancy delivery outcomes and a time-to-event analysis was performed using the Kaplan-Meier survival curve and Cox regression. Poisson regression was performed adjusting for race, ethnicity, insurance status, maternal age at index delivery, and index prepregnancy body mass index.

A total of 268 patients met the inclusion criteria, with 70 (26.1%) having a documented unintended hysterotomy extension during second-stage cesarean delivery. Of those with extensions, 26/70 (37.1%) were inferior/involved the cervix and 44/70 (62.9%) extensions were lateral to the hysterotomy. In unadjusted analysis, rates of subsequent sPTB were similar in the unintended extension group compared to the no-extension group (8/70, 11.4% vs. 11/198, 5.6%; risk ratio [RR] 2.06; 95% CI, 0.86-4.91; p = 0.10). However, in the adjusted Poisson regression, patients with an extension in their index cesarean delivery had higher risk of sPTB in their subsequent pregnancy (adjusted incidence rate ratio [aIRR], 2.48; 95% CI, 1.04-5.92). We did not detect a difference in risk for subsequent sPTB by location of the hysterotomy extension. Subsequent mode of delivery did not differ between the two groups, and no cases of uterine rupture were observed in the entire cohort.

Hysterotomy extensions during second-stage cesarean delivery may be associated with increased risk of sPTB in subsequent pregnancies. Despite sample size limitations, these findings provide a basis for future investigation in this obstetric subpopulation.