The association among fetal head position, fetal head rotation and descent during the progress of labor: a clinical study of an ultrasound-based longitudinal cohort study in nulliparous women.

Objectives: To elucidate the effects of the timing of fetal head rotation on the labor progress and outcomes.

Methods: A paired ultrasound measurement was performed at each of the three stages of labor: latency stage, active stage, and full-cervical-dilatation stage. The measurements included fetal head position, head-perineum distance (HPD) and the angle of progression (AOP).

Results: A total of 46 pregnancy women were included and a total of 102 effective measurements were collected. The cases in occipital anterior position were all eutocia. The rate of cesarean section in the left transverse occipital group was the highest (15.7 %, 3/19). There were 13 cases (37.1 %) with fetal head rotation occur during active phase, changing from occipital transverse to anterior. Ten cases (28.6 %) rotated in the second stage of labor. The average rotation degree of occipital transverse to anterior position was 62.6°. When AoP <95°, 100 % of the women were occipital transverse; When AoP ≥125°, 66.7 % was occipital anterior. The rate of oxytocin utilization and epidural analgesia in the occipital posterior group was higher than that in the other groups (71.4 and 85.7 %, respectively).

Conclusions: Occipital transverse is the most common fetal head position in the early stage of labor and fetal head rotation occurs mostly in the active phase and the second stage of labor. Sufficient time should be given in labor management for women that who tried vaginal delivery without contraindications.