METHODS
This prospective,
longitudinal
observational, single-center study was conducted in the Women’s Hospital
at Zhejiang University School of Medicine in Hangzhou, China, between
May
2020 and November 2020. Nulliparous women with a singleton pregnancy in
a cephalic presentation at term (37 or more full weeks of gestation)
attempting vaginal birth were eligible for the study. Women were
excluded if they were under 18 years of age, had intrauterine death or
had emergencies (e.g., premature placental abruption, uterine rupture,
cardiac disease of New York Heart Association (NYHA) grade 3 or 4,
eclampsia). We also excluded the cases if they required cesarean
deliveries purely because of fetal distress. The study was approved by
the local ethics and research committees (IRB-20200148-R). Written
consent was obtained from the women who agreed to participate.