Progestogens in the prevention of miscarriage

Progestational agents are often prescribed to prevent threatened miscarriage progressing to miscarriage, and subsequent miscarriages in recurrent pregnancy loss. Progestogens affect implantation, cytokine balance, natural killer cell activity, arachidonic acid release and myometrial contractility. A recent Cochrane review reported that progestogens were effective for treating threatened miscarriage with no harmful effects on mother or fetus. The results were not statistically different when vaginal progesterone was compared to placebo, (RR=0.47, 95% CI 0.17-1.30), whereas oral progestogen (dydrogesterone) was effective (RR=0.54, CI 0.35-0.84). The review concluded, that the small number of eligible studies, and the small number of the participants, limited the power of the metaanalysis. A later metaanalysis of five randomised controlled trials of threatened miscarriage comprised 660 patients. The results of 335 women who received dydrogesterone were compared to 325 women receiveing either placebo or bed rest. There was a 47% reduction in the odds ratio for miscarriage, (OR=0.47, CI 0.31-0.7). There was a 13% (44/335) miscarriage rate after dydrogesterone administration compared to 24% in control women. Recurrent miscarriage affects approximately 1% of women of child bearing age. A metaanalysis of progestational agents shows a 26% increase in the live birth rate. Again, dydrogesterone was associated with a more significant increase in the live birth rate than the other progestogens included in the metaanalysis.