Hormone Progesterone Has Limited Benefit In Preventing Preterm Birth, NEJM Studies Say

Main Category: Pregnancy / Obstetrics
Also Included In: Endocrinology
Article Date: 06 Aug 2007 - 6:00 PDT

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Treatment with the hormone progesterone reduces the risk of premature birth for a woman with a short cervix but does not prevent premature birth for a woman who is pregnant with twins, according to two separate studies published Thursday in the New England Journal of Medicine, Reuters reports. According to Reuters, doctors have known for years that giving progesterone to women who have had one premature infant often prevents a second preterm delivery; however, 90% of premature infants are born to women have not had one previously.

Cervix Study
For one of the studies, Eduardo Fonseca of King's College Hospital in London and colleagues examined women at eight hospitals who had a cervix 15 millimeters or less in length, which is less than half the average length of a cervix (Emery, Reuters, 8/1). Researchers measured 24,620 pregnant women and found that 413, or 1.7%, of the women had a short cervix. The study found that about 19% of the women who used vaginal progesterone suppositories gave birth prematurely, compared with a 34% premature birth rate among women who were given a placebo (McCullough, Philadelphia Inquirer, 8/2).

The study also found that the risk of delivering an infant with complications was 41% lower when taking progesterone, but the actual figures were too small to be statistically significant, Reuters reports. "The findings of our study provide support for a strategy of routine screening of pregnant women by ultrasonographic measurement of cervical length and the prophylactic administration of progesterone to those with a short cervix," the researchers said (Reuters, 8/1).

Twins Study
For the study of twins, Dwight Rouse of the University of Alabama-Birmingham and colleagues at 14 clinics gave weekly injections of progesterone or a placebo to healthy women pregnant with twins starting at 16 to 20 weeks' gestation and ending at 35 weeks' gestation. According to the study, 41.5% of pregnancies among the 325 women who received progesterone injections resulted in premature delivery or fetal death before 35 weeks' gestation, compared with 37.3% among the 330 who received a placebo. The researchers concluded that treatment with progesterone did not reduce the rate of preterm birth in women pregnant with twins (Rouse et al., NEJM, 8/2). Twin births have increased from 1.9% in 1980 to about 3.2% today in part because of fertility treatments, Reuters reports (Reuters, 8/1).

Anthony Sciscione -- who led research for the study at Drexel University College of Medicine and is now chief of maternal-fetal medicine at Christiana Care Health System -- said, "We were disappointed by the results," but added, "Nobody's going to give up." Catherine Spong -- a researcher at NIH, which funded the progesterone study in women carrying twins -- said, "Preterm birth is a major problem with many different pathways leading to it. Multiple gestation is just one pathway." Spong added, "We were all hopeful. But I don't think it's effective in twin pregnancies" (Philadelphia Inquirer, 8/2).

In a related NEJM editorial, Jim Thornton of the University of Nottingham wrote, "Even if progesterone therapy is effective for some women who are at risk of preterm labor, reliable evidence is needed about long-term effects on the children before it could be widely recommended" (Reuters, 8/1).

An abstract of Fonseca's study is available online.

An abstract of Rouse's study is available online.

The editorial is available online.

Reprinted with kind permission from http://www.kaisernetwork.org. You can view the entire Kaiser Daily Health Policy Report, search the archives, or sign up for email delivery at http://www.kaisernetwork.org/dailyreports/healthpolicy. The Kaiser Daily Health Policy Report is published for kaisernetwork.org, a free service of The Henry J. Kaiser Family Foundation. © 2005 Advisory Board Company and Kaiser Family Foundation. All rights reserved.

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