Key messages

• Giving progestogen medication likely makes little to no difference to the chances of miscarriage or live birth for women who have previously had miscarriages for no known reason.

What is recurrent miscarriage?

Early pregnancy loss, also known as miscarriage, generally occurs in the first trimester (the first 13 weeks of pregnancy). For some women and their partners, miscarriages can happen several times. This is also known as having recurrent miscarriage. While there are sometimes causes found for miscarriages, there are often no clear reasons why it happens.

What are progestogens, and why might they be used?

The hormone called progesterone prepares the womb (uterus) to receive and support the newly fertilized egg during the early part of pregnancy. It has been suggested that some women who miscarry may not make enough progesterone in the early part of pregnancy. Supplementation with medications that act like progesterone (called progestogens), which may be natural or synthetic, has been suggested as a possible way to prevent recurrent miscarriage. Having miscarriages can be both physically and emotionally difficult for women and their partners. Finding a therapy to help reduce recurrent miscarriage could help them avoid a miscarriage and have a live baby.

What did we want to find out?

We wanted to find out if giving a progestogen in early pregnancy would be better than giving nothing to improve:

• miscarriage (hoping to reduce this);

• live birth rate (hoping to increase this);

• other problems for moms and babies (hoping to reduce these problems, such as low birthweight or needing special care).

What did we do?

We searched for published studies that included women who had experienced recurrent miscarriage and either gave them progestogen treatment or no treatment (or a 'dummy' pill). We excluded studies of women who had in-vitro fertilization (IVF) fertility treatment.

What did we find?

We found nine studies that enrolled a total of 1426 women with a history of recurrent miscarriage. Eight of the studies contained information we could use, for a total of 1276 women. These studies found that giving progestogen medication early in pregnancy to women with recurrent miscarriage probably makes little or no difference to their chance of miscarriage. We did not find that giving the progestogen medication by mouth, as a shot (injection), or in the vagina, was likely any better than any of the other ways. The studies also showed that giving progestogen to women with prior recurrent miscarriage probably made little or no difference to the chance of having a live baby in the current pregnancy. We are uncertain about the effect of progestogen on the chances of preterm birth, newborn death, newborn birth defects, or stillbirth.

What are the limitations of the evidence?

We found evidence was often from older studies, many of which were somewhat small. This also meant that some of the details about how some of the studies were done were not clear. Not all of the studies provided data about all the effects that we were interested in.

How up to date is the evidence?

This updated review searched the evidence on 25 July 2024.