For women who have had multiple miscarriages, a safe and inexpensive progesterone treatment may increase their chances of completing a pregnancy. In a new study published in the journal Fertility and Sterility, two-thirds of women who used the hormonal supplement before pregnancy successfully delivered babies, despite having had at least two previous pregnancy losses.

Progesterone has been shown to help stabilize the inner lining of the uterus called the endometrium, an important factor for healthy embryo development. Progesterone supplements (also known as micronized progesterone) have been recommended for more than 50 years for women struggling with infertility, but there’s been less research on how it might benefit women who get pregnant but then miscarry.

Researchers from the University of Illinois at Chicago and Yale University recruited 116 women who had lost at least two early pregnancies, and tested their levels of nCyclinE, a molecular marker for endometrial health. Those with abnormal levels were then prescribed progesterone supplementation, to be inserted vaginally, twice a day during the second half of their menstrual cycles.

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The intervention seemed to help. In the progesterone group, 68% of the women had subsequent successful pregnancies, compared to 51% of those who did not receive the hormone.

The researchers believe that the progesterone caused the endometrium to secrete more nutrients, which serve as food for an embryo in its first weeks of development. (Women who became pregnant continued taking progesterone until the 10-week mark.)

Lead author Dr. Mary Stephenson, director of the recurrent pregnancy loss program at the University of Illinois Hospital and Health Sciences, says that women who have suffered multiple pregnancy losses should talk to their doctors about progesterone supplementation.

“We now know that, for some women, the use of progesterone in the second half of the menstrual cycle is associated with a higher likelihood of taking home a baby, and that is really good news,” says Dr. Stephenson. “We also know that progesterone is safe in early pregnancy, easy to use and inexpensive.”

Progesterone can be prescribed in several forms, including creams, capsules and pills that are inserted vaginally with an applicator. Women can self-administer these treatments, and they are usually covered by insurance, says Dr. Stephenson.

However, there are many possible causes of recurrent pregnancy loss, a condition that affects up to one in 20 women. Before deciding on a treatment option, she cautions, patients should undergo a thorough evaluation to determine what strategies might work for them.

In fact, the new research suggests that testing women for nCyclinE and other biomarkers may help doctors determine which patients would benefit from progesterone supplementation.

Co-author Dr. Harvey J. Kliman, director of the reproductive and placental research unit in the department of obstetrics, gynecology and reproductive sciences at Yale School of Medicine, invented the patented test for nCyclinE levels used in the study.

“We initially created the Endometrial Function Test to identify women with infertility,” Dr. Kliman said in a press release. “This study has shown that the EFT can also be an important tool for patients with recurrent pregnancy loss.”

The study was published today in the journal Fertility and Sterility. Dr. Stephenson says she is in the early stages of developing a randomized clinical trial, which is needed to validate her early findings and influence any official recommendations for women who have had multiple miscarriages.

In the meantime, those women should talk with their doctors, says Dr. Stephenson. “We’ve been using vaginal progesterone for some time for recurrent pregnancy loss,” she says. “We know that it’s a reasonable strategy—one that should be discussed, risks and benefits, between patient and physician.”

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