Progesterone treatment lowers the risk of preterm birth in women with a short cervix.
Progesterone is a naturally occurring hormone that plays an important role in maintaining pregnancy. It's believed that a short cervix -- a known risk factor for preterm birth -- may be a sign of a shortage of progesterone.
This study included 458 women with a short cervix (10-20 millimeters) who were randomly assigned to receive either a vaginal gel with progesterone or a placebo between the 19th and 23rd week of pregnancy.
The rate of preterm delivery at less than 33 weeks pregnancy was 8.9 percent for women who received the progesterone treatment and 16.1 percent for those who received the placebo. There were also differences between the two groups in rates of preterm births before 28 and 35 weeks of pregnancy.
The researchers also found that infants born to women who received the progesterone treatment had a lower rate of respiratory distress syndrome than those born to women who received the placebo -- 3 percent vs. 7.6 percent.
Women with a short cervix can be identified by ultrasound, according to the researchers.
The study, published online in the journal Ultrasound in Obstetrics and Gynecology, was conducted by researchers at the U.S. National Institute of Child Health and Human Development and colleagues at 44 medical centers worldwide. It also involved New Jersey-based Columbia Laboratories Inc, which makes a progesterone gel.
In the United States, preterm delivery is a significant problem, with 12.8 percent of infants born preterm annually, according to the March of Dimes.