Study co-author Dr. Catherine Y. Spong of the Eunice Kennedy Shriver National Institute of Child Health and Human Development said each year, 12.5 percent of U.S. infants are born preterm -- increasing infant risk of death and if the baby survives, he or she might have an increased risk breathing and vision problems, learning disabilities and cerebral palsy.
In February 2011, the U.S. Food and Drug Administration approved the use of 17 alpha-hydroxyprogesterone caproate, a synthetic form of progesterone, to reduce the chances of preterm birth in women pregnant with a single fetus who had delivered a single infant early in a previous pregnancy.
The study involved 600 women pregnant for the first time assigned at random to receive either the hormone or a placebo. The researchers found that rates of preterm birth were about the same among women who received a weekly injection of 17 alpha-hydroxyprogesterone and those who received a placebo.
"Studying each at risk group alone allows us to identify which treatments are effective in specific situations," Spong said in a statement. "This study shows the need to test 17 alpha-hydroxyprogesterone among the different categories of women at risk for preterm delivery, rather than assuming that because it was shown to be effective in one group, that it would be effective in another."