Intrapartum sonographic evaluation of fetal head descent in relation to maternal position: comparison between dorsal...

To evaluate the impact of maternal position on the sonographic indicators of fetal head descent in the latent phase of the second stage of labor.

This was a prospective, single-center, cohort study conducted at the University of Parma, Parma, Italy, between November 2023 and October 2024, including a consecutive series of non-anomalous, low-risk, singleton pregnancies at ≥ 37 + 0 weeks' gestation in the latent phase of the second stage of labor. Sonographic assessment of the fetal head position and station was performed by two dedicated and trained research midwives; the former was evaluated using transabdominal ultrasound, and the latter by measuring the head-to-perineum distance (HPD) and the angle of progression (AoP) on transperineal ultrasound. The sonographic indicators of fetal head station were measured between uterine contractions, with the mother first in the dorsal lithotomy position and then in the kneeling squat position. The Wilcoxon signed-rank test and linear mixed-effects models were applied to compare the measurements of AoP and HPD between the dorsal lithotomy and kneeling squat positions. Generalized additive models (GAMs) were utilized to describe the relationship and estimate the predicted change in AoP and HPD when transitioning from the dorsal lithotomy to the kneeling squat position.

Overall, 55 patients underwent measurement of the sonographic indicators of fetal head station in both maternal positions. Occiput posterior position was recorded in only two cases (3.6%), with the remaining cases in occiput anterior position. Both the Wilcoxon signed-ranked test and linear mixed-effects models showed that HPD was significantly shorter when measured in the kneeling squat compared with the dorsal lithotomy position (30.3 ± 8.2 vs 35.5 ± 8.9 mm, P < 0.01). Consistently, a wider mean AoP was recorded in the kneeling squat compared with the dorsal lithotomy position (135.4° ± 15.1° vs 125.6° ± 11.9°, P < 0.01). GAMs highlighted an increasing non-linear relationship between measurements of AoP and HPD obtained in the dorsal lithotomy and kneeling squat positions.

During the latent phase of the second stage of labor, maternal mobilization into upright positions, such as the kneeling squat position, is associated with more favorable sonographic indicators of fetal head station. However, this study supports such findings only in the event of fetal occiput anterior position. Sonographic studies with larger cohorts are warranted to evaluate the clinical relevance of these findings, as well as the role of maternal mobilization in the second stage of labor in relation to the position of the fetal occiput. © 2026 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.