New Test May Help Pinpoint Time of Birth

With a simple test, doctors soon may be able to predict whether apregnant woman will give birth within 48 hours.

The test screens for a protein known as fetal fibronectin thatappears in the vagina of women who are about to deliver, according toa study published recently in the American Journal of Obstetrics andGynecology.

Doctors look for the protein by taking a small sample of mucusfrom the woman's vagina or cervix.

Only 6 percent of women actually deliver on their due date,according to the study's lead author, Dr. Regine Ahner of theUniversity of Vienna in Austria.

"From both a medical and psychological point of view . . .accurate determination of the actual onset of labor and deliverywould be desirable, especially in women who have gone past theirexpected due date," Ahner wrote.

The Austrian researcher and his colleagues suspect that fetalfibronectin is released into a woman's cervix and vagina afterimperceptible uterine contractions begin. The weak contractions maycause fetal tissue to separate from the uterine tissue, releasing theprotein.

The researchers followed the pregnancies of 100 women who hadpassed their due dates, and collected mucus samples from the women tolook for traces of fibronectin.

Within 48 hours after the samples were collected, 41 of thewomen gave birth. Four of these women were excluded from the studybecause they either had a Caesarean section or had labor induced. Ofthe remaining 37 patients, 30 had positive tests for fibronectin,while seven did not.

A total of 59 patients delivered later than 48 hours aftersampling, according to the researchers, and three of these patientswere excluded from the study because they required C-sections. Ofthe remaining 56 patients, 51 had a negative fibronectin test, whilefive produced positive tests.

This means that the test was accurate 86 percent of the timewhen it was positive, and 88 percent of the time when it wasnegative.

Experts in maternal-fetal medicine criticized the study for itsexclusion of the women who needed C-sections or had labor induced.The study does not explain why the women needed those procedures, yetthose factors may have been important to the study's results, theresearchers said.

"The exclusion of so many patients may give one a more positiveimpression of this test than the data would allow," said Dr. FrankWitter, an associate professor of gynecology and obstetrics at theJohns Hopkins University School of Medicine in Baltimore.

But while the test is not accurate enough to predict the exactmoment a woman will go into labor, it may give women a better idea ofwhen they will deliver when combined with other information, Wittersaid.

A New York expert said the test will be most useful in helpingto predict which women will go into premature labor. For instance,doctors could use the test to confirm their suspicions when theydetect signs of early labor.

"This study backs up earlier work that showed that fetalfibronectin can be detected in patients about to undergo laborearly," said Dr. Daniel M. Lasser, an assistant professor of medicinein the department of obstetrics and gynecology atColumbia-Presbyterian Medical Center.

"Despite all the advances in obstetrical care, very little hasbeen done in terms of preventing preterm labor," Lasser said. "Theonly thing that has advanced is care of the preterm baby."

If doctors can determine which women are at high risk of anearly delivery, they may be able to find ways to slow the process,Lasser said.