To explore the association between fetal head station at the diagnosis of the 2nd stage of labor and the second stage duration and the risk for operative delivery. A retrospective cohort study of all singleton vertex deliveries in a single tertiary center (2010-2016). Women were grouped according to fetal head station upon diagnosis of second stage: above (S<0), at the level (S=0) and below (S>0) the level of the ischial spine. The duration of the 2nd stage and the risk for operative delivery was compared between the study groups. Analysis was stratified by parity. 1) Of 70,021 deliveries during the study period, 35,592 (50.8%) met the inclusion criteria. Amongst, 4,727 (13.3%) were diagnosed with fetal head above, 12,698 (35.7%) were at the level and 18,167 (51.0%) with fetal head below the ischial spine. Of all, 19,539 (54.8%) were nulliparous. 2) The median(IQR) duration of the 2nd stage was 99(48-159) and 16(9-39) minutes for nulliparous and multiparous, respectively. The rate of epidural anesthesia was 86.8% and 77.3% and the rate of spontaneous vaginal delivery was 83.0% and 96.2%, respectively (p<0.001). 3) For nulliparous women, the median duration (95%CI) of the 2nd stage was the shortest in the S>0 group following by S=0 and S<0 groups (149(144-153), 131(128-133) and 73(71-74) minutes, respectively; p<0.001). In multiparous, S>0 group had the shortest duration (14(13-14)) followed by S<0 and S=0 (15(14-16) and 23(22-23) minutes, respectively; p<0.001) (Figure). 4) In multivariable analysis, after controlling for maternal age, gestational age at delivery, pre-pregnancy BMI, spontaneous onset of labor, epidural anesthesia, meconium and first stage duration, the risk for operative delivery was the lowest in the S>0 group (Table). In the S=0 group there was increased risk for cesarean delivery (p<0.05) but not for operative vaginal delivery as compared to the S<0 group (Table). Fetal station at the first diagnosis of the second stage is significantly associated with the duration of the second stage and is significantly correlated with the risk for operative delivery in both nulliparous and multiparous women.View Large Image Figure ViewerDownload Hi-res image Download (PPT)