Study: Current tests for predicting spontaneous preterm births, not accurate

Research Triangle Park, NC—Spontaneous preterm birth is a leading cause of infant mortality. According to the World Health Organization, 15 million babies are born early each year, 1 million of whom die due to complications.

A new report published in the Journal of the American Medical Association found that tests currently used to predict the risk of spontaneous preterm birth in women who are having their first child—cervical length and levels of fetal fibronectin, a protein thought to “glue” the amniotic sac to the lining of the uterus—yielded low accuracy results.

“Previous studies suggest that women with a short cervix or high levels of fetal fibronectin in the vagina may be at an increased risk of premature birth,” said Corette Parker, DrPH, study author and senior biostatistician at RTI International. “Our findings, however, show that these tests are not very predictive of preterm birth in first time mothers, so the routine use of these tests for screening should no longer be supported.”

This report is part of the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be (nuMoM2b), for which RTI serves as the data coordinating and analysis center.

“As the data center, we collaborate with clinical investigators and scientists to develop the study protocol,” Parker said. “We also develop data collection forms and management systems, train study staff in standard procedures, monitor recruitment and data quality, and conduct the statistical analysis in consultation with clinical investigators.”

The study followed 9,410 women throughout their pregnancy. The women had ultrasounds to measure cervical length during their second and third trimester. Fetal fibronectin tests were conducted three times during pregnancy.

Of the women studied, 91 percent had term births, 3.6 percent had medically indicated preterm births, and 5 percent had spontaneous preterm births. Among the women with spontaneous preterm birth, 8 percent had a cervical length of 25mm or less at 16 to 22 weeks and 23.3 percent at 22 to 30 weeks. Fetal fibronectin levels at 16 to 22 weeks identified 7.3 percent of women who would deliver prematurely, and 8.1 percent at 22 to 30 weeks.

From these and related findings reported in the article, researchers concluded that the tests did not identify enough preterm births to support routine screening of first-time pregnancies.