Objective: In November 2003 ACOG recommended the use of progesterone to prevent preterm delivery (PTD) in women at high risk. Aim of this review is to investigate whether subsequent literature supports the use of progesterone.

Data sources: A search in PubMed, Medline, EMBASE, and the Cochrane Trials Register from January 2003 to October 2008 was conducted. Search terms were preterm delivery, preterm labo(u)r, preterm birth, progesterone, 17α-hydroxyprogesterone caproate, pregnancy.

Review methods: Randomized clinical trials that assessed high-risk women were consi-dered. PTD rates and neonatal outcomes were compared between groups. Odds Ratio (OR) and 95% Confidence Intervals (CI) were calculated using the Mantel–Haenszel fixed-effects model and the DerSimonian–Laird random-effects model.

Results: Four articles were included in analysis. PTD was significantly reduced by progesterone (276/812, 34% vs. controls; 272/650, 42%, p=0.01; OR=0.49; 95% CI: 0.24–0.84). Neonatal outcomes were different between progesterone and controls in regard to birth weight <1500g (44/426, 10% vs. 48/276, 17% respectively, p=0.02, OR=0.60, 95% CI: 0.38–0.93) and neonatal death (16/740, 2% vs. 23/580, 4%, respectively, p=0.04, OR=0.50, 95% CI: 0.26–0.96).

Conclusion: The administration of progesterone provides beneficial effects for the prevention of PTD in women at high risk.