Progesterone supplements in the first trimester of pregnancy do NOT improve outcomes in women with a history of unexplained recurrent miscarriages.
Five years after it began, the results of the PROMISE (progesterone in recurrent miscarriage) trial have now been published (1).
Clear but disappointing
These results are clear, they are very important – and they are bound to be disappointing to many women and couples – and to those who care for them. We had all hoped that the trial would show that progesterone is an effective treatment for those considering pregnancy after previous losses, but sadly we now know it is not.
The study of 826 women with previously unexplained recurrent miscarriage showed that those who received progesterone treatment in early pregnancy were no less likely to miscarry than those who received a placebo (or dummy treatment). This was true whatever their age, ethnicity, medical history and pregnancy history.
There is important good news here too. The first is that nearly two-thirds of the women in the trial had their baby, whether they had progesterone or the placebo. So even without treatment, the chances of a healthy pregnancy after unexplained recurrent miscarriage are better than some might expect.
The trial results also showed that there were no harmful effects of progesterone treatment for women or for their babies. That is very important information for women taking progesterone for other reasons, such as fertility treatment or for those taking part in the PRISM (progesterone in threatened miscarriage) trial.
Finally, after more than 60 years of debate, we now know that progesterone treatment in early pregnancy isn’t the answer for women with unexplained recurrent losses. And that means that researchers can now direct their efforts to exploring and testing other treatments that really can reduce the risk.
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(1) Coomarasamy A et al. A Randomized Trial of Progesterone in Women with Recurrent Miscarriages. N Eng J Med 2015 Nov 26;373(22):2141-8. DOI: 10.1056/NEJMoa1504927.