Preventing Preterm Birth

BACKGROUND: According to the March of Dimes, in 2000, 467,201 babies were born preterm, representing 12 percent of the more than 4,058,000 births in the United States. Today 1,300 babies in the United States will be born prematurely. The rate of premature birth increased 27 percent between 1981 and 2000.

Most pregnancies last around 40 weeks. Babies born before 37 completed weeks of pregnancy are called premature or preterm. Of those babies born preterm, the majority (about 83 percent) are born between 32 and 36 weeks of gestation. About 10 percent are born between 28 and 31 weeks of gestation, and about 6 percent are born at less than 28 weeks of gestation. All babies born preterm are at risk for serious health problems, but those born earliest are at greater risk of long-term disabilities and death. Advances in obstetrics and neonatology, have improved the chances for survival for even these smallest babies. Very premature babies have the highest risk of death and lasting disabilities, such as mental retardation, cerebral palsy, lung and gastrointestinal problems, and vision and hearing loss.

PRETERM BIRTH PREVENTION: Researchers at the University of North Carolina at Chapel Hill studied more than 450 pregnant women with a well-documented history of spontaneously giving birth prior to 37 weeks. Of these women, whose pregnancies were 16 to 20 weeks along, 306 were randomly assigned to treatment with weekly injections of 17P, a progesterone hormone drug. Another 153 women received placebo injections and served as a control group. Injections continued until 36 weeks gestation. The hormone used in the study was 17-alpha-hydroxyprogesterone caproate, also known as 17P. Small studies from the 1970s and 1980s suggested that the therapy might prevent recurrent preterm births, but this is the first large-scale rigorous trial to confirm these earlier findings.

Treatment with 17P significantly reduced the risk of preterm birth at less than 37, 35 and 32 weeks gestation. The risk of preterm term birth prior to 37 weeks was reduced by 34 percent, and the risk for delivery at less than 32 weeks was reduced by 42 percent. Babies who are born at less than 32 weeks are most at risk, in terms of health problems and mortality.

PROGESTERONE: John Thorp, M.D., professor of obstetrics and gynecology at the University of North Carolina, Chapel Hill, says he's not sure why the progesterone treatments prevent preterm birth, but says past studies have shown a drop in progesterone levels in women right before birth. Researchers theorized that by maintaining normal levels of progesterone, premature birth might be avoided.

After birth defects, premature birth is the leading cause of infant mortality in the Unite States. Premature babies tend to have underdeveloped brains and lungs and can spend weeks or months in neo-natal intensive care units. Neo-natal intensive care has increased survival rates, but it is expensive and infants can still suffer long-term health problems, even into adulthood. Dr. Thorp says the full 16-week course of this preventative treatment costs about as much as one day in a neo-natal intensive care unit. The progesterone drug itself is not new. It is FDA-approved and was used extensively in the 1950s and 1960s as a synthetic progestin.

FOR MORE INFORMATION, PLEASE CONTACT:
John Thorp, M.D.
University of North Carolina, Chapel Hill
(919) 966-1601
E-mail: thorp@med.unc.edu