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 methods: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 September 2011) and bibliographies of all located articles for any additional studies.
Selection criteria: Randomised or quasi-randomised 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, assessed trial quality and extracted the data. Data were checked for accuracy.
Main results: We included four studies (421 participants) in the meta-analysis. In three studies all the participants met the inclusion criteria and in the fourth study, we included only the subgroup of participants who met the inclusion criteria in the meta-analysis. There was evidence of a reduction in the rate of spontaneous miscarriage with the use of progestogens compared to placebo or no treatment (risk ratio (RR) 0.53; 95% confidence interval (CI) 0.35 to 0.79). There was no increase in the rate of antepartum haemorrhage (RR 0.76; 95% CI 0.30 to 1.94), or pregnancy-induced hypertension (RR 1.00; 95% CI 0.54 to 1.88) for the mother. The rate of congenital abnormalities was no different between the newborns of the mothers who received progestogens and those who did not (RR 0.70; 95% CI 0.10 to 4.82).
Authors' conclusions: The data from this review suggest that the use of progestogens is effective in the treatment of threatened miscarriage with no evidence of increased rates of pregnancy-induced hypertension or antepartum haemorrhage as harmful effects to the mother, nor increased occurrence of congenital abnormalities on the newborn. However, the analysis was limited by the small number and the poor methodological quality of eligible studies (four studies) and the small number of the participants (421), which limit the power of the meta-analysis and hence of this conclusion.