Progesterone supplements taken during the first trimester of pregnancy do not improve outcomes in women with a history of unexplained, recurrent miscarriages, researchers reported in the New England Journal of Medicine.

The progesterone in miscarriage treatment (PROMISE) trial – a randomized, double-blind, placebo-controlled trial – enrolled 826 women aged 18 to 39 at hospitals across the United Kingdom and the Netherlands. A total of 398 women were given progesterone supplements; 428 women were in the placebo group.

At completion, nearly two-thirds of all women in the trial gave birth. The live birth rate was 65.8% in the treatment group, and 63.3% in the placebo group. Those who received the progesterone treatment early in their pregnancy were no less likely to miscarry than were those who received a placebo, regardless of age, ethnicity, or medical and pregnancy history.

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“We had hoped that this research would confirm progesterone as an effective treatment,” said Professor Arri Coomarasamy, MBChB, MD, MRCOG, DFFP, Professor of Gynecology at the Institute of Metabolism and Systems Research at the University of Birmingham, UK. “Though disappointing, it does address a question that has remained unanswered since progesterone was first approved as a treatment back in 1953.”

However, Professor Coomarasamy did note that, despite the unexpected findings, the PROMISE trial has resulted in a number of other positive outcomes: no significant negative effects of progesterone treatment were recorded for either mothers or their babies – essential for women taking progesterone as a fertility treatment.

“Furthermore,” added Professor Coomarasamy, “the PROMISE trial created a solid network of doctors, nurses, and midwives across the UK and beyond, all committed to miscarriage research.”


  1. Coomarasamy A, Williams H, Truchanowicz E, et al. A randomized trial of progesterone in women with recurrent miscarriages. N Engl J Med. 2015;373(22):2141-2148. doi: 10.1056/NEJMoa1504927