Around 1 in 8 babies in the United States is born premature, increasing the risk for long hospital stays and health problems down the road.

But knowing which first-time moms are more likely to go into labor preterm is not easy.

“The largest risk factor for preterm birth is a history of preterm birth, which by definition, first-time mothers don’t have,” said Dr. Erin Clark, an assistant professor of obstetrics and gynecology at the University of Utah Health Sciences Center. “Predicting which first-time mothers will deliver early is very difficult.” READ MORE.