Risk factors for uterine incision extension during cesarean delivery

Unintentional extension of uterine incision is a known complication during cesarean delivery estimated to occur in 4-8% of cesarean deliveries. The aim of this study was to examine risk factors associated with unintentional uterine incision extension and to assess which of them are independent risk factors for this condition.

We conducted a retrospective cohort study at a large public university tertiary referral center between 2003 and 2017. Included were women who underwent cesarean delivery during this time period. Demographic, medical, obstetrical and surgical data were collected. The primary outcome was the presence of uterine incision extension during cesarean delivery. Secondary outcomes included detection of risk factors associated with uterine incision extension. A multivariate analysis was additionally performed to identify general and labor related risk factors for unintentional extension of uterine incision among patients that underwent cesarean delivery during second stage of labor.

During the study period, 25,879 cesarean deliveries performed in our medical center were assessed. Out of them, 731 (2.8%) cases of unintended uterine incision extension were identified. Women in this group had high rates of full cervical dilatation and increased maternal hemorrhage. Assessment of incision extension direction revealed that two-thirds of extensions were lateral, mostly unilateral. Median size of the extension was 2.7 ± 1.2 cm.Independent parameters associated with unintended uterine incision extension included nulliparity, vertex presentation, epidural anesthesia and cesarean section indication. Further analysis including cesarean deliveries performed during the second stage of labor revealed 397 (15.3%) cesarean deliveries in which incision extension was noted and 2205 (84.7%) cesarean deliveries without incision extension. Following multivariate analysis performed in women who underwent cesarean delivery during second stage of labor, two independent parameters associated with unintended uterine incision extension remained significant - past cesarean delivery and failed vacuum attempt.

Vacuum extraction attempt and previous cesarean delivery are independent risk factors for uterine incision extension in women undergoing cesarean delivery during the second stage of labor. We also showed the majority of these extensions to be lateral.