Progesterone for women with threatened miscarriage (STOP trial): a placebo-controlled randomized clinical trial.

Study Question: In women with threatened miscarriage, does progesterone supplementation until the completion of the first trimester of pregnancy increase the probability of live birth?

Summary Answer: In women with threatened miscarriage, 400 mg vaginal progesterone nightly, from onset of bleeding until 12 weeks, did not increase live birth rates.

What Is Known Already: Limited evidence has indicated that vaginal micronized progesterone may make little or no difference to the live birth rate when compared with placebo in women with threatened miscarriage. Subgroup analysis of one recent randomized trial reported that in women with bleeding and at least one previous miscarriage, progesterone might be of benefit.