Progestogens may be given to pregnant women whose children were previously born premature, in order to avoid a subsequent early birth, according to a Vanderbilt study in Obstetrics & Gynecology.

Researchers found that when these women are given progestogens while expecting a single child, they receive benefits from the additional hormone.

Progestogens are natural or synthetic forms of progesterone, a female hormone that naturally increases while a woman is pregnant. The name refers to its purpose in maintaining pregnancy (pro-gestational), although it is also present at other phases of menstrual cycles.

34 previous studies of women who were given progestogens for prior preterm births, preterm labor, multiple gestations, short cervix, or other forewarnings were analyzed. The studies took place between January 1966 and October 2011, while each study consisted of over 20 women who received the medication by injection, vaginally or orally.

Experts discovered that progestogens do not benefit women carrying twins or triplets. One particular study in 2009, published in The Lancet, showed evidence that progesterone treatment does not help pregnant women avoid early preterm birth with twins.

There was also no evidence that showed progestogens to be effective for all other uses, meaning that clinical care should not yet use this research as a guide for treatment in those cases.

Although this latest report has some important findings, more research is still needed, said Frances E. Likis, DrPH, N.P., CNM, leading author and research assistant professor of Medicine.

Likis continued:

“While we know that women have progesterone levels that go up in early pregnancy and remain elevated, we still don’t understand why giving extra progestogens would help them stay pregnant. The pharmaceutical effects are not well understood.”

The United States is known to have a very high preterm birth rate. “We haven’t been able to move that number very well, and although it’s gone down somewhat in past years, it’s not a dramatic drop,” she said.

Vanderbilt’s longer report, along with the systematic review, is being released by the AHRQ (Agency for Healthcare Research and Quality). It goes into detail on the differences of how to administer progestogens and the various effects it has for preterm birth.

Clinicians normally give progestogens to pregnant women at the start of the second trimester through 37 weeks gestation or until birth. The majority are given an injection once a week, although some receive the medication vaginally. Very few women prefer to take it orally.

Answering whether progestogens are generally beneficial simply isn’t possible, according to Likis. Since females are given progestogens for various reasons, this review set out to determine how effective the hormone therapy is, rather than why it is administered.

She said:

“Having had a previous preterm birth is different from having twins, and that’s how clinicians make decisions. They don’t just look at women and say ‘you’re at risk,’ they say ‘what is your risk factor?

In order to find out what the complications related to progestogen therapy might be, a larger study is required. There’s relatively little evidence about whether babies had complications, and there’s also very little information about long-term health effects on the infant. There’s a lot more that needs to be studied. There’s a lot of work to be done.”

Written by Sarah Glynn