Progesterone for Maintenance Tocolytic Therapy After Threatened Preterm Labor: A Randomized Controlled Trial

Although patients in whom preterm labor is arrested are at an increased risk of recurrence, it is not clear whether maintenance tocolytic treatment is appropriate. In this randomized trial, the ability of supplemental vaginal progesterone in a daily dose of 400 mg to prevent recurrences was assessed in 70 women at 24–34 weeks’ gestation who presented with symptoms of threatened preterm labor and in whom uterine activity was arrested. Progesterone was chosen for study because it can maintain a quiescent uterus and has been widely used for the primary or secondary prevention of preterm delivery. Preterm labor was defined as more than 6 contractions in 30 minutes along with cervical shortening or dilation. Thirty-seven women received vaginal progesterone while 33 were untreated. Baseline characteristics were similar in the 2 groups. Latency to delivery was significantly longer in progesterone-treated women (36.1 versus 24.5 days). There also were significant differences favoring vaginal progesterone therapy in the incidence of respiratory distress syndrome (10.8% versus 36.4%); birth weight (3101 versus 2609 gm); and low birth weight (27% versus 51.5%). No significant group differences were found with respect to recurrent preterm labor, admission to intensive care, or neonatal sepsis. There were no cases of neonatal necrotizing enterocolitis or intraventricular hemorrhage, and no infants exhibited congenital malformations. In addition, no adverse effects were observed in women treated with progesterone. The use of vaginal progesterone suppositories following successful tocolysis was associated with a longer predelivery interval in this study, but it did not significantly reduce the frequency of readmission for preterm labor.