Progesterone - The Hormone's Role in Pregnancy

Can Progesterone Supplementation Help Reduce Miscarriage or Preterm Labor?

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Progesterone is a hormone involved in women's menstrual cycles and in maintaining the lining of the uterus to support a pregnancy. The hormone plays many important roles during pregnancy, and it may be involved in some miscarriages.

The Role of Progesterone In Pregnancy

Progesterone is a sex hormone involved in menstruation and pregnancy. Levels of the hormone increase in the second half of the menstrual cycle, after ovulation, and usually remain high if a woman gets pregnant.

In the later part of the menstrual cycle, known as the luteal phase, progesterone helps build up the lining of the uterus to support a pregnancy. If conception doesn't occur, progesterone levels plummet and the uterine lining breaks down, resulting in menstrual bleeding.

During pregnancy, progesterone prepares the uterus to receive and support a fertilized egg. The hormone helps blood vessels form in the lining of the womb and stimulates glands in the lining to secrete nutrients needed by the embryo. The hormone also keeps the uterine wall from contracting so the fertilized egg can successfully adhere there.

Progesterone also keeps more eggs from maturing during pregnancy and brings about breast tissue changes that get a woman's body ready for breastfeeding.

Progesterone for Miscarriage Prevention

The corpus luteum, a group of cells formed in the ovary after an egg is released during ovulation, secretes most of a woman's progesterone.

At around the third month of pregnancy, the placenta begins to secrete progesterone to supplement the corpus luteum.

Some doctors suspect that low progesterone levels early in pregnancy contribute to many miscarriages. They have therefore hypothesized that progesterone supplementation during early pregnancy might help prevent miscarriages.

This treatment is often used to prevent miscarriages in women undergoing infertility treatment.

Unfortunately, the evidence does not appear to support the use of progesterone to prevent miscarriages.

In 2013, Australian researchers published a review of studies on combined estrogen (another important hormone) and progesterone for preventing miscarriage. (This combination has been used in the past to save threatened pregnancies.) Only two studies met their criteria, and neither showed a benefit of the combined therapy. The reviewers concluded that more research was needed.

The same year, American researchers reviewed 14 studies where progestogens (the group of hormones that includes progesterone) were given to women in the first 20 weeks of pregnancy. When all women were considered together, there was no benefit of progestogens over placebo or no treatment for preventing miscarriages. However, when the researchers looked only at women with recurrent miscarriages, a benefit for preventing miscarriages did emerge.

The researchers cautioned that these studies were not well-designed and that future studies were needed.

Then, in 2015, a study published in the New England Journal of Medicine reported disappointing results. The study specifically looked at progesterone supplementation in women with recurrent unexplained miscarriages. The women who got placebo or no treatment had the same rate of live births as women who used twice-daily progesterone vaginal suppositories in the first trimester. The rates of ectopic pregnancy, miscarriage and stillbirth were the same across the board.

There was, however, a silver lining: More than 60 percent of the women in the study - all of whom had experienced at least three recurrent unexplained miscarriages before - had healthy pregnancies.

Progesterone for Preventing Preterm Birth

Progesterone can help prevent preterm birth, and a synthetic progesterone, or progestin, is now officially approved for this use.

The Food and Drug Administration (FDA) approved a progestin drug injection called Makena (hydroxyprogesterone caproate) in 2011 for use during pregnancy. It's used to reduce the risk of preterm birth in women carrying one child who have with a history of spontaneous preterm delivery. 


Lim, C.E.D., Ho, K.K.W., Cheng, N.C.L., Wong, F.W.S. Combined oestrogen and progesterone for preventing miscarriage. Cochrane Database of Systematic Reviews 2013, Issue 9.

Haas, D.M., Ramsey, P.S. Progestogen for preventing miscarriage. Cochrane Database of Systematic Reviews 2013, Issue 10.

Coomarasamy, A., Williams, H., Truchanowicz, E., et al. (2015). A Randomized Trial of Progesterone in Women with Recurrent Miscarriages. New England Journal of Medicine

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