(499) Fetal Head Station at Second Stage Onset Predicts Delivery Outcomes in Nulliparous Women

To investigate the association of fetal head station at the onset of the second stage of labor with delivery outcomes, specifically the duration of the second stage and the mode of delivery in nulliparous women.

Study Design:

Retrospective cohort of all nulliparous women with singleton gestations who delivered at a single high-volume tertiary center between 2012 and 2020. All women delivered at term ( >37 gestational weeks) and progressed to the second stage of labor. Fetal head station at the onset of the second stage was categorized as below (S > 0), at (S=0), or above (S< 0) the ischial spines. Delivery outcomes, including mode of delivery and second-stage duration, were compared across these groups.

Results:

12,877 nulliparous women were included. Women with the fetal head below the ischial spines (S > 0) had a higher rate of vaginal delivery (6019, 77.84%) and shorter second-stage duration compared to women with the head at (437, 64.17%,) or above (3184, 69.82%) the ischial spines. The likelihood of cesarean delivery was low across all groups (S < 0 36 5.29%, S=0 102 2.29%, S > 0 49 0.63%). A significant association was found between fetal head station at second stage onset, and the duration of the shorter second-stage of labor (p < 0.01). The median duration of the second stage was 2.52, 2.17 and 1.32 hours for s< 0, s+0 and s > 0 respectively.

Conclusion:

Fetal head station at the onset of the second stage of labor is an independent predictor of delivery outcomes in nulliparous women. A lower fetal head station is associated with a shorter second-stage duration and a higher likelihood of vaginal delivery.