March 25, 2017 0136 GMT
The commonly used tests assessed the shortened length of the cervix and the presence of fetal fibronectin — a glue-like protein that holds the amniotic sac to the uterus — in early pregnancy as risk factors for preterm birth, or birth before 37 weeks gestation, UPI wrote.
The new study by NIH researchers suggested those markers are not indicative of an increased risk of preterm birth.
Researchers screened 9,410 pregnant women as part of the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-be.
Participants had ultrasound testing to measure cervical length at 16 to 22 weeks of pregnancy and again from 22 to 31 weeks.
Fetal fibronectin tests were also performed at six and 14 weeks, 16 to 22 weeks and 22 to 30 weeks gestation.
About eight percent of the women tested at 16 to 22 weeks had a shortened cervix and went on to deliver spontaneously before 37 weeks.
Nearly 23.3 percent of women who were tested at 22 to 30 weeks had a shortened cervix and delivered prematurely.
The fibronectin test showed just 7.3 percent of women who delivered prematurely had high fibronectin levels at 16 to 22 weeks, while 8.1 percent of women delivered prematurely had high fibronectin levels at 22 to 30 weeks.
Researchers concluded that results of the tests, whether combined or alone, were not enough to support routine screening of preterm birth risk in first-time pregnancies.
Dr. Uma Reddy, a researcher at the Pregnancy and Perinatology Branch of NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development, said, "These methods of assessing women in their first pregnancy do not identify most of those who will later go on to have a spontaneous preterm delivery.
"There is a need to develop better screening tests that can be performed early in pregnancy."