MONDAY, Jan. 31, 2005 (HealthDayNews) -- Using progesterone therapy to prevent preterm labor shows tremendous promise, at least among women at high risk for delivering prematurely, researchers report.
If all high-risk women had received the injections in 2002, it would have cut the nation's preterm birth rate by 2 percent that year, according to a study reported in the February issue of Obstetrics and Gynecology.
"That translates to about 10,000 preterm births prevented, so we feel optimistic," said study author Joann R. Petrini, director of the March of Dimes Perinatal Data Center.
The treatment involves receiving weekly injections of 17 alpha-hydroxyprogesterone caproate, a derivative of the hormone progesterone.
Researchers from the U.S. Centers for Disease Control and Prevention, the National Institute of Child Health and Human Development and others joined with the March of Dimes to assess the national impact of the progesterone derivative, known as 17P.
The new analysis is based on criteria from an earlier randomized controlled trial reported in the June 12, 2003, issue of the New England Journal of Medicine. That study showed a 33 percent reduction in preterm births among women with a history of spontaneous -- meaning unexplained or unintended -- preterm birth who got weekly injections of 17P.
Acknowledging the apparent benefits of the drug for high-risk women, the American College of Obstetricians and Gynecologists (ACOG) issued an opinion in October 2003 urging physicians to restrict progesterone use to pregnant women with a documented history of a previous spontaneous preterm birth. Further studies are needed to evaluate the use of progesterone in patients with other high-risk obstetric factors, it said.
Preterm birth is a leading cause of infant mortality and long-term disability, according to the March of Dimes. In the United States, more than 480,000 births -- or 12 percent of all live births each year-- are preterm, meaning they occurred before 37 weeks of gestation. Between 1982 and 2002, the national rate of these births rose 27 percent.
Yet decades of research have yielded no intervention that is broadly effective in preventing preterm deliveries, the study authors said. From that perspective, 17P appears to be something of a breakthrough.
"That's what the excitement is about: it's the first drug that appears to help preterm labor," said study co-author Dr. Nancy S. Green, medical director of the March of Dimes. There's no other treatment on the horizon that promises to help prevent preterm labor, she added.
To estimate the national impact of 17P, researchers used 2002 birth certificate data augmented by vital statistics from two states. They included women who were pregnant with a single child, who had a documented history of spontaneous preterm birth and who began receiving prenatal care within the first four months of pregnancy. By estimating the number and rate of those births, they were able to predict the effect 17P might have.
In 2002, there were about 30,000 recurrent preterm births among women who fit the eligibility criteria for 17P, the authors estimate. That is based on 22 percent rate of recurrent spontaneous preterm births.
By administering 17P, the overall preterm birth rate would slip to 11.8 percent, preventing about 10,000 preterm births, they found.
"It's not a panacea," conceded study co-author Dr. Richard H. Schwarz, vice chairman of obstetrics and gynecology at Maimonides Medical Center in New York City. "The reason we're keen on this is that this appears to be one area in which we do have something that seems to work."
Doctors at Maimonides and across the country, in fact, are beginning to use it for patients who fit the high-risk profile, he added. One limitation: 17P is not commercially available; a physician must order it through a compounding pharmacy, which specializes in making special drug formulations.
Meantime, the potential of 17P among a broader population of women remains unknown. "More has to be done to know whether this drug, 17P, could be useful in other situations where there's a risk of premature births," including women pregnant with twins, Green said.
Check out the March of Dimes for more on preterm labor.