This Way Out: Fetal Descent During Labor

Diane J. Angelini, EdD, CNM, FACNM, FAAN, NEA-BC

Progression of fetal descent and pelvic station varied substantially in a contemporary U.S. population.

The definition of “normal” labor progression has changed with the evolution of obstetric practice (NEJM JW Womens Health Dec 16 2010). In a retrospective cohort study at one teaching hospital, researchers derived average curves for cervical dilation and fetal descent in 4618 women (33% nulliparous) with vaginal term deliveries sometime between 2004 and 2008. The study sample was stratified by parity and type of labor (spontaneous vs. induced or augmented).

Multiparous women achieved faster fetal descent than nulliparous women at almost all pelvic stations. Labor was spontaneous in 39% of participants overall. Fetal descent was faster in spontaneous labor than induced or augmented labor even after adjustment for parity, maternal body-mass index, and neonatal weight. The 95th percentile for time to descend one station level was as long as 12.5 hours (between stations −2 and −1 in nulliparous women) — yet all women in spontaneous labor achieved vaginal birth. The vast majority of women were at 0 station or lower at complete cervical dilation. For women who were multiparous, in spontaneous labor, or both, descent curves steepened after −1 station had been reached.

Citation(s):

Graseck A et al. Fetal descent in labor. Obstet Gynecol 2014 Mar; 123:521.