Assessment of labor progress via digital examination is considered the standard of care in most delivery rooms. However, this method can be stressful, painful, and imprecise, and multiple examinations increase the risk for chorioamnionitis. Intrapartum ultrasound was found to be an objective, noninvasive tool to monitor labor progression.

This study aimed to investigate whether, among nulliparous women, the use of intrapartum ultrasound can reduce the rate of intrapartum fever by reducing the number of digital examinations.

This was a prospective, randomized controlled trial in term nulliparas admitted with prelabor rupture of membranes, induction of labor, or in latent phase of labor with a cervical dilation of <4 cm. Women were randomized into 1 of the following 2 arms: (1) labor progress assessed by ultrasound, avoiding digital examinations as much as possible; and (2) control group in which labor progression was assessed according to the regular protocol. Before the study, all labor ward physicians underwent training in intrapartum ultrasound.

A total of 90 women were randomized to the ultrasound group and 92 were randomized to the control group. When compared with the control group, the ultrasound group had significantly lower rates of intrapartum fever (11.1% vs 26.1%; P=.01), clinical chorioamnionitis (3.3% vs 16.5%; P>.01), and histologic chorioamnionitis (2.2% vs 9.8%; P=.03). The median number of digital examinations was significantly lower in the ultrasound group (5; interquartile range, 4–6) than in the control group (8; interquartile range, 6–10; P<.01). The median number of digital examinations per hour in the ultrasound group was significantly lower than in the control group (0.2 vs 0.4; P<.01). The induction rates, time from admission to delivery, mode of delivery, Apgar score at 5 minutes, and neonatal intensive care unit admission rates did not differ significantly between the groups.

The use of intrapartum ultrasound lessens the total number of digital examinations needed to be performed during labor and, consequently, the incidence of intrapartum fever and chorioamnionitis are reduced. No adverse effects on labor progression and short-term maternal or neonatal outcomes were noted.