This study aims to investigate the threshold effect of labor duration on adverse outcomes associated with cesarean sections in pregnant women with gestational hypertension and preeclampsia (GH-PE). This study conducted a retrospective cohort study on 1188 pregnant women who delivered at our hospital from January 1, 2022, to December 31, 2024. The effect of the threshold value of the labor duration for successful vaginal delivery among pregnant women with GH-PE was analyzed through curve fitting. And compare the adverse outcomes of emergency cesarean section before and after the threshold of labor duration. Among the 1188 samples, all were primiparous women who underwent cervical balloon dilation for the induction of labor. In pregnant women with GH-PE, an analysis of the threshold effect of cervical dilation duration from 2 to 4 cm on successful vaginal delivery shows that the shorter the time taken for cervical dilation, the higher the success rate of vaginal delivery. However, once this time exceeds 3.1 hour, the success rate of vaginal delivery basically remains stable. Meanwhile, it was also found that in pregnant women with GH-PE who underwent emergency cesarean section during delivery, when the duration for cervical dilation from 2 to 4 cm exceeded 3.1 hour, the incidence of postpartum hemorrhage (odds ratio: 5.97, 95% confidence interval: 1.38-25.78) and the volume of postpartum hemorrhage were higher compared to those with a duration of ≤ 3.1 hour. For primiparous women with GH-PE undergoing cervical balloon induction, the inflection point for successful vaginal delivery may be when the cervical dilation reaches 2 to 4 cm within 3.1 hour, and transfer to cesarean section before the inflection point might be possible to reduce the incidence of postpartum hemorrhage.