New Blood Tests Promise to Better Predict Early Labor

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Researchers say a new test for pregnant women is more than 80 percent accurate in predicting preterm births, the leading cause of death for children under 5 in the United States. (iStock)

Two new blood tests promise pregnant women an easier, more affordable way of predicting their risk for an premature delivery. The blood tests, developed by Stanford University School of Medicine and UC San Francisco, look for specific biomarkers in the mother's bloodstream.

Preterm delivery, which occurs when a baby is born before the 37th week of pregnancy, is the leading cause of death for children under 5 in the United States.

The Stanford-led study, predicts the risk of preterm birth using fetal RNA found in the mother's blood, while the UCSF study focuses on inflammation markers.

There is currently one blood test on the market that screens for preterm risk, but it comes with serious limitations, according to Laura Jelliffe-Pawlowski, co-author of the UCSF study and director of the UCSF California Preterm Birth Initiative. The costly test screens only for spontaneous preterm births. About three quarters of preterm births occur spontaneously while 25 percent are induced due to medical complications.

But for practitioners like Dr. Juan Gonzalez, a perinatologist at UCSF Medical Center, knowing whether a pregnancy is high-risk is not all that helpful without being able to adequately treat the problem.


"A patient can have a positive result but we need to know which intervention is the right intervention. This is a great finding but now we need those next steps, which are studies that focus on interventions.  That's the part we don’t really know."

Dr. Yvonne Butler Tobah, a Mayo obstetrician, called the developments "groundbreaking" but warned that further research is required before it can be instituted clinically.

Causes of Preterm Birth

The causes of pre-term birth are not well understood, but doctors look for certain traits associated with the risk, according to

"So we know things like hypertension and diabetes are associated with preterm birth," says Jelliffe-Pawlowski. "And also the kinds of things that the test picks up, like inflammation, is associated with preterm birth."

The UCSF study also looked at income and age of the pregnant women, two factors that exert an independent influence on bodily inflammation and placenta function, according to Jelliffe-Pawlowski. Mothers over the age of 34 are found to be at higher risk of inflammation levels.

An underlying infection, exposure to environmental toxins, stress, or chronic ailments like diabetes, can all trigger an inflammatory response in pregnant women, a condition that has potential to  induce an early pregnancy.

A subset of women who test positive for preterm risk have a severe pregnancy complication called preeclampsia. The potentially fatal condition is characterized by high blood pressure and organ failure in the mother.

Treatments are Limited

Current medical treatments are typically limited to cases of preeclampsia, and involve taking aspirin, which Jelliffe-Pawlowski says reduces the occurrence of preeclampsia by up to 30 percent.

For women with a prior history of preterm delivery, there is a progesterone supplement that is currently offered to decrease the risk, according to Tobah.

"Prior preterm birth confers about a two fold increased risk," she said.

But outside of this limited category of high-risk pregnancies, there isn't much doctors can recommend in the way of decreasing preterm risk -- outside of bed rest, according to Gonzalez.

And preeclampsia comprises just 15 percent of all preterm births, making preventative care for the great majority of preterm cases all the more urgent, says Gonzalez.

"Before doctors start running these tests, we really need to know what are we going to tell these women besides, 'You’re at risk,'" he says.

But for the researchers involved in both studies, affordability and accessibility played an important  role in the tests' development.

"While the current available treatments are not great, I do think they have some effect," says co-author Mads Melbye, a  professor in medical epidemiology at the University of Copenhagen, Denmark. "For instance, if you know a woman is likely to deliver a preterm baby, you would likely refer her to a specialized hospital. And certainly the knowledge alone is important."

For Jelliffe-Pawlowski, helping pregnant women in disadvantaged communities was a huge motivator for developing the test.

"What we hear from women in the community, particularly black and Latina women, is what's really important to them, is knowing their risk," says Jelliffe-Pawlowski. "It's not necessary that we fix it, but there's an opportunity to communicate risk with women so they can be taken care of appropriately."

And Melbye says accurate tests are important, since inaccurate estimates can lead to unnecessary treatments such as the induction of labor or Cesarean sections.

Measuring Risk Through RNA

The Stanford-led study, published last week in the journal Science,  measured cell-free fetal RNA in the mothers' bloodstream to determine the due date and preterm risk.

The researchers compared the blood results of women who had healthy pregnancies with those found to be at high risk for preterm delivery. They accurately predicted six of eight preterm cases and wrongly classified only one of 26 full-term cases.

But the Stanford test is a pilot study based on a limited number of women.

"The next step will be to apply the findings to large clinical trials," says Melbye. "The study is just the first in a series of studies that allows us to look at the different outcomes of pregnancy. The hope is that it will lead to healthier and safer pregnancies."

Measuring Risk Through Inflammation

The UCSF test focused on 63 biomarkers in the mother's bloodstream related to inflammation and placenta function. From there, researchers narrowed the test down to 25 biomarkers that  together help to predict the chances of an early pregnancy.

The study, published in the May issue of Journal of Perinatology, is more than 80 percent accurate in predicting preterm births in women who are between 15 and 20 weeks pregnant.

In cases of high risk pregnancies, the test was nearly 90 percent accurate.

The UCSF test, which took five years to develop,  is based on ten years of research by Jelliffe-Pawlowski's team. Researchers took blood samples from 400 women during their second trimester.

Researchers hope their blood tests will lead to better preventative treatments for women found to be at high risk of preterm birth.


"We want to make sure that we're developing something that has the potential to help all women, including those most in need," says Jelliffe-Pawlowski.