Maternal outcomes according to fetal head station at diagnosis of the second stage of labor

Objective This study determines the association between fetal head station (FHS) at the diagnosis of the second stage of labor and adverse maternal outcomes. Methods This retrospective cohort study was conducted at a single university‐affiliated tertiary medical center from 2011 to 2023, including singleton vertex deliveries at ≥ 37 weeks of gestation. Participants were stratified by parity FHS at the diagnosis of the second stage: nulliparous (Group A: above the ischial spines, Group B: at the ischial spines, Group C: below the ischial spines) and multiparous (Group α: above the ischial spines, Group β: at the ischial spines, Group γ: below the ischial spines). The composite maternal outcome included red blood cell transfusion, third‐ or fourth‐degree perineal tears, postpartum fever ≥38°C, intensive care unit admission, rehospitalization, or surgery within 6 weeks postpartum. Results Of 146 194 deliveries, 64 349 were eligible (42 987 nulliparous; 21 362 multiparous). Among nulliparas, 8.0%, 34.9%, and 57.2% began the second stage above, at, and below the spines, respectively; corresponding multiparous rates were 14.7%, 27.8%, and 57.5%. Nulliparas in Group A had higher transfusion rates (2.7% vs. 1.9% and 1.4%; P < 0.001) and higher composite morbidity (5.6% vs. 4.6% and 4.1%; P < 0.001). In multivariable regression, FHS above the ischial spines remained independently associated with increased risk for red blood cell transfusion (odds ratio [OR] 1.5, 95% confidence interval [CI] 1.1–1.9) and composite morbidity (OR 1.3, 95% CI 1.1–1.5). No association was observed among multiparous women. Conclusion In nulliparous women, a higher FHS at the onset of the second stage of labor is independently associated with an increased risk of postpartum complications, irrespective of second stage duration.