Vaginal Progesterone Supplementation in the Management of Preterm Labor: A Randomized Controlled Trial

The primary objective in this study was to evaluate the effects of vaginal progesterone supplementation for the prolongation of the latency period in preterm labor. The secondary objectives were to evaluate gestational age at delivery, rates of preterm birth less than 34 and 37 weeks, obstetric outcomes, maternal compliance with medication use, and side effects.

A randomized controlled, unblinded trial was performed. Ninety women with preterm labor occurring at 24 to 34 weeks were either randomized to a vaginal progesterone group (44 women) receiving tocolytic and antenatal corticosteroids treatment combined with vaginal micronized progesterone (400 mg everyday) or to the no-progesterone group (46 women) receiving tocolytic and antenatal corticosteroids treatment only.

Latency periods were more prolonged in the vaginal progesterone group than in the no-progesterone group (32.8 ± 18.7 vs. 25.8 ± 22.7 days, p = 0.045). Gestational age at delivery in the vaginal progesterone group was also higher than in the no-progesterone group (37 vs. 35 weeks, p = 0.027). There were significant reduction rates of preterm birth less than 34 weeks (13.6% vs. 39.1%, p = 0.012), low birth weight (29.5% vs. 50%, p = 0.048), neonatal respiratory distress syndrome (13.6% vs. 37%, p = 0.021), and neonatal intensive care unit admission (6.8% vs. 28.3%, p = 0.017).

Combined treatment with vaginal progesterone 400 mg could prolong the latency period in preterm labor when compared with no progesterone.