Randomized trial of endovaginal ultrasound in preterm premature rupture of membranes

To assess the effect of weekly endovaginal ultrasound on the incidence of maternal infection and the time from rupture to delivery in women with preterm premature rupture of membranes (PROM).

Women with singleton pregnancies complicated by preterm PROM at 24-34 weeks' gestation were assigned randomly to groups having endovaginal ultrasound or no vaginal sonography. Along with the standard expectant management, the endovaginal-ultrasound group had weekly vaginal probe ultrasound scans. Power analysis based upon expected maternal infection required a sample size of 45 patients in each group.

Forty-seven and 45 subjects were assigned to the no-probe and probe groups, respectively. The latency period, defined as days from rupture to delivery, was 9.8 and 11.7 days for the no-probe and probe groups, respectively (95% confidence interval -5.9, 2.1). There were no significant differences in the incidence of chorioamnionitis (28% and 20%), endometritis (6% and 9%), or neonatal infection (17% and 20%). The mean latency period in women who went into spontaneous labor and whose initial cervical length was 3.0 cm or less was 9.4 days, compared with 11.0 days if the cervix exceeded 3.0 cm, a nonsignificant difference. There were three neonatal deaths, all in the probe group and none directly related to infection.

Endovaginal ultrasound in patients whose pregnancies are complicated by preterm PROM does not appear to increase the incidence of maternal infection.