Prophylactic administration of progesterone by vaginal suppository to reduce the incidence of spontaneous preterm birth in women at increased risk: a randomized placebo-controlled double-blind study.

OBJECTIVE The purpose of this study was to evaluate the effect of prophylactic vaginal progesterone in decreasing preterm birth rate in a high-risk population. STUDY DESIGN A randomized, double-blind, placebo-controlled study included 142 high-risk singleton pregnancies. Progesterone (100 mg) or placebo was administered daily by vaginal suppository and all patients underwent uterine contraction monitoring with an external tocodynamometer once a week for 60 minutes, between 24 and 34 weeks of gestation. Progesterone (n = 72) and placebo (n = 70) groups were compared for epidemiologic characteristics, uterine contraction frequency, and incidence of preterm birth. Data were compared by chi(2) analysis and Fisher exact test. RESULTS The preterm birth rate was 21.1% (30/142). Differences in uterine activity were found between the progesterone and placebo groups (23.6% vs 54.3%, respectively; P <.05) and in preterm birth between progesterone and placebo (13.8% vs 28.5%, respectively; P <.05). More women were delivered before 34 weeks in the placebo group (18.5%) than in the progesterone group (2.7%) (P <.05). CONCLUSION Prophylactic vaginal progesterone reduced the frequency of uterine contractions and the rate of preterm delivery in women at high risk for prematurity.