Birmingham, UK—Bleeding in early pregnancy has a strong link with pregnancy loss, a heartbreaking outcome for expectant mothers and their families. New research suggests that giving the hormone progesterone might help a subset of those women.

The PRISM trial involved 4,153 pregnant women who presented with early pregnancy bleeding to 48 hospitals across the United Kingdom. Participants were randomly assigned to receive either progesterone or a placebo.

Results published in the New England Journal of Medicine showed that overall among women with bleeding in early pregnancy, progesterone therapy administered during the first trimester did not result in a significantly higher incidence of live births than placebo. It did show some benefit, however, for those who had early pregnancy bleeding and had previously suffered a miscarriage, according to a study authors.

The women, who were being treated at 48 hospitals across the UK, were randomly assigned by computer into one of two groups—one group of 2,079 women were given progesterone, while the other group of 2,074 women were given a placebo.

“Miscarriage is a common complication of pregnancy, affecting one in five women, and vaginal bleeding in early pregnancy is associated with a one in three risk of miscarriage,” explained coauthor Adam Devall, PhD, senior clinical trial fellow at the University of Birmingham and manager of Tommy’s National Centre for Miscarriage Research, adding, “Several small studies have suggested that administering progesterone, a hormone essential for maintaining a pregnancy, may reduce the risk of miscarriage in women presenting with early pregnancy bleeding.”

Devall said the PRISM trial “was undertaken to answer a very important research question; whether progesterone given to pregnant women with threatened miscarriage would increase the number of babies born after at least 34 weeks of gestation when compared with a placebo.”

While the results might have been disappointing overall, the researchers found that there was a 4% increase in the number of babies born to the women in the study who were given progesterone and had previously had one or two miscarriages compared with those given a placebo. In fact, they said, of the 777 women given progesterone who had previously had one or two miscarriages, 591 (76%) went on to have a live birth, compared with 534 women out of 738 in the placebo group (72%).

The study found an even greater benefit for the women who previously had suffered three or more miscarriages, labeled as “recurrent.” Researchers said they had a 15% increase in the live birth rate in the progesterone group compared with the placebo group—of the 137 women taking part in the trial who had previously had three or more miscarriages, 98 (72%) went on to have a live birth, compared with 57% (85 out of 148) women in the placebo group.

“The role of progesterone in women with early pregnancy bleeding has been studied and debated for about 60 years, however, what we have previously lacked is high quality evidence,” noted lead author Arri Coomarasamy, MB, ChB, MD. “The largest study before the PRISM trial had less than 200 participants; whereas our study had more than 4,000 participants and was of very high quality, which means we can be confident in our findings.

“Our finding that women who are at risk of a miscarriage because of current pregnancy bleeding and a history of a previous miscarriage could benefit from progesterone treatment has huge implications for practice. This treatment could save thousands of babies who may have otherwise been lost to a miscarriage.”

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