Story highlights

Two new studies use blood tests to predict a pregnant woman's preterm birth risk

"Diagnostic tools to predict the risk of preterm birth are limited," an expert says, but that could change soon

CNN  — 

Researchers are looking into the possibility of using blood tests to predict a woman’s risk of premature birth, which could change the future of prenatal care.

A pregnant woman’s risk of delivering early can depend on factors such as a previous preterm birth, certain pregnancy or medical complications, preeclampsia, stress or diabetes. A woman can also have a premature birth even if she has no known risk factors.

“It’s really intriguing to be able to identify when a woman is at higher risk than the general population for a serious complication like preterm birth. That would allow us to focus on them in a way we can’t do right now,” said Dr. Larry Rand, an associate professor and the Marc and Lynne Benioff Endowed Chair in Maternal Fetal Medicine at the University of California, San Francisco.

“On the flip side, in terms of predicting (medically) indicated preterm birth, what you’re really predicting is the likelihood that mom or baby will develop a complication like preeclampsia or growth restriction that may require ending the pregnancy early in order to keep mom and baby safe,” said Rand, who is also principal investigator of the California Preterm Birth Initiative.

Two separate studies – one published last month in the Journal of Perinatology and another published Thursday in the journal Science – are among the latest efforts to develop such a test. Rand is an author of the Journal of Perinatology study.

The tests described in those studies are still in very early stages of development, and much more research is needed to determine and validate their accuracy, safety and efficacy – but they represent where preterm birth testing seems to be heading.

In the United States, preterm birth affected about one of every 10 infants born in 2016, according to the Centers for Disease Control and Prevention.

Around the world every year, an estimated 15 million babies are born too early – before 37 completed weeks of gestation – and this number is rising, according to the World Health Organization. Preterm birth complications are the leading cause of death among children under 5, responsible for about 1 million deaths worldwide in 2015.

In 2010, the 10 countries with the highest total numbers of preterm births were India, China, Nigeria, Pakistan, Indonesia, the United States, Bangladesh, Philippines, Democratic Republic of Congo and Brazil, according to a study published in the Lancet in 2012.

However, some of those data might not be entirely accurate since some women in low-income countries lack the resources to determine the gestational age of a pregnancy.

“Especially in low- and middle-income countries with really high preterm birth rates and huge neonatal mortality rates, one of the biggest problems is, there is no ultrasound, and women are not empowered to keep track of their last menstrual cycle. It’s often taboo to keep track of or talk about your period,” Rand said.

“That is one of the biggest problems we have worldwide, and lots of folks have been working on trying to find another way – ideally an inexpensive test – to figure out what the gestational age is for any given pregnancy.”

What testing for preterm birth risk looks like

The blood test described in the Journal of Perinatology aimed to predict the risk of preterm birth among pregnant women with and without preeclampsia, a condition characterized by high blood pressure.

The test, developed and studied in 400 women during their second trimester, screened for 25 biomarkers or substances in the blood that were signs of inflammation and immune system activation, as well as certain protein levels, indicative of a possible preterm birth risk.

Those 25 biomarkers were selected from a panel of 63 that had been shown to be related to preterm birth or preeclampsia.

The researchers found that screening for those biomarkers, along with taking into account a pregnant woman’s age and poverty status, could identify the risk of preterm birth with or without preeclampsia in most of the women in the study during their second trimester.

“Our test was able to predict 80.3% of women who went on to have any preterm birth, at 15 to 20 weeks gestation,” said Laura Jelliffe-Pawlowski, an associate professor and director of Precision Health and Discovery at the University of California, San Francisco’s Preterm Birth Initiative, who was first author of the study.

She added that because the test identified women who are at high risk for preterm birth with preeclampsia – identifying about 95% of women who went on to have preterm birth with preeclampsia before 32 weeks – it offers an opportunity for intervention, such as for starting those moms-to-be on a low-dose aspirin to help lower their risk of preeclampsia.

“Our test also suggests that women with elevated risks based on the test might benefit from additional testing,” she said. “I think our test could be rapidly translated into clinical settings if it is found to validate in a larger set of pregnancies. The next step for us is to identify the right partners for conducting a large, rapid, clinical validation study.”

In other words, more research is needed.

As for cost, Jelliffe-Pawlowski thinks the test could probably be run for about $50 to $100.

“A low-cost, highly accurate test has the most potential for helping blunt the current epidemic of preterm birth in the United States and around the world, an epidemic that disproportionally affects women of color, especially black women, who are as much as twice as likely to deliver preterm than their white peers,” she said.