Using a portable device to monitor contractions in pregnant women does not help detect early labor and prevent premature delivery, a study found.
The study suggests other screening tests for premature labor do not work very well either.
Premature birth is a leading cause of death and disability among newborns. Doctors try to catch premature labor early enough to delay it so that the fetus can fully develop.
One device often used is called a home uterine activity monitor. Worn on a belt around the abdomen, the machine records contractions of the uterus and sends the information via the telephone to a nurse for evaluation. Previous studies suggested the monitors are not very good at identifying those who will delivery prematurely.
In the current study, researchers in 11 cities gave monitors to 306 pregnant women, most at high risk for a premature birth, and looked at the pattern and frequency of their contractions.
They found only a slight difference in the number of contractions between women who delivered prematurely and those who didn't. "That difference was so small that it was practically useless," said Dr. Jay D. Iams of Ohio State University, who headed the study.
The research, funded by the National Institute of Child Health and Human Development, is reported in Thursday's New England Journal of Medicine.
"Preterm labor and preterm delivery are such complex issues, and this study is definitely showing that," said Dr. Catherine Spong of the institute's pregnancy and perinatology branch.
Nearly 12 percent of infants are born premature, or at less than 37 weeks of gestation. Woman are more likely to deliver early if they have had a preterm birth, are carrying more than one fetus or have other conditions such as high blood pressure. If premature labor is detected, doctors prescribe antibiotics, medication to slow the contractions or bed rest.
Most of the women in the study were at high risk because they had had at least one premature delivery. They used the monitor for two hours a day at least twice a week until delivery or 37 weeks.
The researchers tried other techniques to detect early labor — measuring the cervix and testing for a protein called fetal fibronectin — and found they, too, are not useful.
"We've got to figure out what's causing this so we can prevent it — not try to prevent it once the process is well on its way to completion," said Dr. Charles J. Lockwood of New York University School of Medicine, who wrote an accompanying editorial.
The monitors used in the study were from Atlanta-based Matria Healthcare Inc., whose chairman and chief executive, Pete Petit, defended the devices as a cheaper alternative to hospitalizing high-risk patients. The monitor and the accompanying analysis cost $100 a day.
He said Matria's monitors have been used by about 500,000 women over the past 14 years.
"There are tremendous clinical improvements and cost-effectiveness that's associated with just prolonging a pregnancy by one or two days or a week," Petit said. "They don't take that into account."
On the Net: New England Journal: www.nejm.org