Objective: We performed a systematic review to assess the benefits and harms of progesterone administration for the prevention of preterm birth in women and their infants.
Data sources: The Cochrane Controlled Trials Register was searched, and reference lists of retrieved studies were searched by hand. No date or language restrictions were placed.
Methods of study selection: Randomized trials comparing antenatal progesterone for women at risk of preterm birth were considered. Studies were evaluated for inclusion and methodological quality. Primary outcomes were perinatal death, preterm birth before 34 weeks, and neurodevelopmental handicap.
Tabulation, integration and results: Eleven randomized controlled trials (2,425 women and 3,187 infants) were included. For women with a history of spontaneous preterm birth, progesterone was associated with a significant reduction in preterm birth before 34 weeks (one study, 142 women, RR 0.15, 95% CI 0.04-0.64, number needed to treat 7, 95% CI 4-17), but no statistically significant differences were identified for the outcome of perinatal death. For women with a short cervix identified on ultrasound, progesterone was not associated with a significant difference in perinatal death (one study, 274 participants, RR 0.38, 95% CI 0.10-1.40), but there was a significant reduction in preterm birth before 34 weeks (one study, 250 women, RR 0.58, 95% CI 0.38-0.87, number needed to treat 7, 95% CI 4-25). For women with a multiple pregnancy, progesterone was associated with no significant difference in perinatal death (one study, 154 participants, RR 1.95, 95% CI 0.37-10.33). For women presenting after threatened preterm labor, no primary outcomes were reported. For women with "other" risk factors for preterm birth, progesterone was not associated with a significant difference in perinatal death (two studies, 264 participants, RR 1.10, 95% CI 0.23-5.29).
Conclusion: Progesterone is associated with some beneficial effects in pregnancy outcome for some women at increased risk of preterm birth.