Background: Miscarriage is a common complication encountered during pregnancy. The role of progesterone in preparing the uterus for the implantation of the embryo and its role in maintaining the pregnancy have been known for a long time. Inadequate secretion of progesterone in early pregnancy has been linked to the aetiology of miscarriage and progesterone supplementation has been used as a treatment for threatened miscarriage to prevent spontaneous pregnancy loss.
Objectives: To determine the efficacy and the safety of progestogens in the treatment of threatened miscarriage.
Search strategy: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (December 2009) and bibliographies of all located articles for any unidentified articles.
Selection criteria: Randomized or quasi-randomized controlled trials that compare progestogen with placebo, no treatment or any other treatment given in an effort to treat threatened miscarriage.
Data collection and analysis: At least two authors assessed the trials for inclusion in the review and extracted the data.
Main results: Two studies (84 participants) were included in the meta-analysis. In one study, all the participants met the inclusion criteria and in the other study, only the subgroup of participants who met the inclusion criteria was included in the meta-analysis. There was no evidence of effectiveness with the use vaginal progesterone compared to placebo in reducing the risk of miscarriage (risk ratio 0.47; 95% confidence interval 0.17 to 1.30).
Authors' conclusions: Based on scarce data from two methodologically poor trials, there is no evidence to support the routine use of progestogens for the treatment of threatened miscarriage. Information about potential harms to the mother or child, or both, with the use of progestogens is lacking. Further, larger, randomized controlled trials on the effect of progestogens on the treatment of threatened miscarriage, which investigate potential harms as well as benefits, are needed.