Women with vaginal bleeding in the first 12 weeks of pregnancy who received progesterone therapy in the first trimester did not experience a difference in pregnancy outcomes compared with women who were administered placebo, according to study results published in the New England Journal of Medicine. 

Investigators for the Progesterone in Spontaneous Miscarriage (PRISM; Current Controlled Trials identifier: ISRCTN14163439) trial, a multicenter, randomized, double-blind analysis, aimed to assess whether progesterone therapy would increase the incidence of live births among women with bleeding during early pregnancy compared with placebo. The primary outcome was a live birth after ≥34 weeks of gestation. 

A total of 4153 women were randomly assigned to receive either vaginal suppositories of progesterone 400 mg twice daily (n=2079) or a matching placebo (n=2074); 97% of participants with available data were included in the primary analysis (n=4038). 

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After at least 34 weeks of gestation, 75% of women from the progesterone cohort and 72% of women from the placebo cohort had live births (relative rate, 1.03). 

At week 12, incidence of ongoing pregnancy for the progesterone group and the placebo group were 83% and 80%, respectively (relative rate, 1.04). The incidence of miscarriage in the progesterone and placebo cohorts was 20% and 22%, respectively (relative rate, 0.91). 

The between-group difference in incidence of maternal or neonatal adverse events was not significant. 

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The investigators noted, however, that the study included some limitations: “[W]e started progesterone treatment only in women who had an intrauterine sac; therefore, our trial cannot provide evidence on the effects of earlier use of progesterone, before a pregnancy sac is visible on an ultrasound examination.” 

They continued: “[A]lthough we found no increase in the risk of congenital abnormalities among babies of women treated with progesterone, the trial was not powered for such rare outcomes.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.


Coomarasamy A, Devall AJ, Cheed V, et al for the PRISM trial. A randomized trial of progesterone in women with bleeding in early pregnancy.N Engl J Med.2019;380(19):1815-1824.