" "This study shows that progesterone therapy is not beneficial for all women at risk for giving birth prematurely," said Duane Alexander, M.D., Director of the NICHD, the NIH institute that supported the research network. "So far, the evidence supports progesterone therapy as a means to reduce preterm birth "only" in women pregnant with a single baby who are at risk for premature delivery because of a prior preterm birth." "

" After the initial study showed progesterone therapy could reduce the likelihood of preterm birth in women carrying a single baby and who had previously given birth prematurely, many physicians began prescribing the therapy for women pregnant with twins and for other categories of women at risk for preterm birth as well. In addition to women carrying two or more babies, and those who have delivered prematurely before, also at risk for preterm delivery are pregnant women having a shortened cervix (the lower part of the uterus) and certain infections of the reproductive tract. "

" The study appears in the August 2, 2007 issue of "The New England Journal of Medicine". "

" A large team of researchers from the NICHD Maternal-Fetal Medicine Units Network, led by Dwight J. Rouse, M.D., Professor of Obstetrics and Gynecology at the University of Alabama at Birmingham School of Medicine, conducted the study. "

" In the study, 655 women pregnant with twins were randomly assigned to receive weekly injections of a placebo or the form of progesterone known as 17-alpha hydroxyprogesterone caproate (17-OHPC), explained Catherine Y. Spong, M.D., Branch Chief of NICHD's Pregnancy and Perinatology Branch, and the NICHD author of the study. "

" Progesterone is a female hormone that is produced in large quantities during pregnancy. Researchers with the Maternal Fetal Medicine Units Network reported in 2003 that weekly injections of progesterone reduced the risk of preterm birth by 34 percent among pregnant women who had given birth prematurely in an earlier pregnancy. "

" Women in the current study were randomly assigned to groups receiving weekly injections of either 250 mg of progesterone or a placebo. The injections started when the women were 16-20 weeks pregnant and continued until the 35th week of pregnancy or until the woman gave birth. Women in both groups had similar characteristics such as age, race, and marital status. "

" The researchers found that the use of progesterone did not reduce premature birth in twin pregnancies when compared with the placebo group: 41.5 percent of women on progesterone treatments delivered prematurely (before 35 weeks) or experienced fetal loss vs. 37.3 percent of women receiving placebo injections. Fetal loss describes the loss of the baby because of such factors as stillbirth or miscarriage, said Dr. Spong. "

" There was no difference between
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