Hormone Progesterone Has Limited Benefit In Preventing Preterm Birth

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Preventing Preterm Birth

Treatment with the hormone progesterone reduces the risk ofpremature birth for a woman with a short cervix but does not preventpremature birth for a woman who is pregnant with twins, according totwo separate studies published Thursday in the New England Journal of Medicine, Reuters reports. According to Reuters, doctorshave known for years that giving progesterone to women who have had onepremature 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 Hospitalin London and colleagues examined women at eight hospitals who had acervix 15 millimeters or less in length, which is less than half theaverage 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 thewomen who used vaginal progesterone suppositories gave birthprematurely, compared with a 34% premature birth rate among women whowere given a placebo (McCullough, Philadelphia Inquirer, 8/2).

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Thestudy also found that the risk of delivering an infant withcomplications was 41% lower when taking progesterone, but the actualfigures were too small to be statistically significant, Reuters reports."The findings of our study provide support for a strategy of routinescreening of pregnant women by ultrasonographic measurement of cervicallength and the prophylactic administration of progesterone to thosewith a short cervix," the researchers said (Reuters, 8/1).

Twins Study

For the study of twins, Dwight Rouse of the University of Alabama-Birminghamand colleagues at 14 clinics gave weekly injections of progesterone ora placebo to healthy women pregnant with twins starting at 16 to 20weeks' gestation and ending at 35 weeks' gestation. According to thestudy, 41.5% of pregnancies among the 325 women who receivedprogesterone injections resulted in premature delivery or fetal deathbefore 35 weeks' gestation, compared with 37.3% among the 330 whoreceived a placebo. The researchers concluded that treatment withprogesterone did not reduce the rate of preterm birth in women pregnantwith 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 leadingto it. Multiple gestation is just one pathway." Spong added, "We wereall 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 Nottinghamwrote, "Even if progesterone therapy is effective for some women whoare at risk of preterm labor, reliable evidence is needed aboutlong-term effects on the children before it could be widelyrecommended" (Reuters, 8/1).
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