Blood tests to predict preterm birth risk raise excitement — and questions
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.
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 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 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.
In 31 healthy pregnant women from Denmark, the researchers measured nine cell-free RNA molecules to predict gestational age with comparable accuracy to ultrasound. Those measurements were based on a machine-learning model that the researchers had previously built to understand what RNA molecules look like in a healthy pregnancy.
In the study, the newly developed test accurately estimated gestational age within 14 days of the actual gestational age at delivery for 45% of women in the study. When ultrasound was used in the study, the ultrasound predicted gestational age in 48% of women.
The 45% accuracy for the blood test was based on an average of samples taken during the second and third trimester. The 48% accuracy for ultrasound was based on ultrasound done during the first trimester of pregnancy.
Then, in 38 women at risk of delivering preterm, the researchers identified seven other cell-free RNA molecules that could accurately distinguish between those women who ended up delivering preterm and those who did not. The test measured up to two months in advance of when any woman delivered preterm, using maternal blood samples drawn late in the second trimester.
Among those 38 women, 25 had full-term and 13 had preterm deliveries. The women who delivered preterm did so between 23 and 33 weeks, Moufarrej said.
“Essentially, the findings are that you can measure gestational age and predict risk of preterm delivery in this pilot study,” Moufarrej said, adding that the study still needs to be replicated in a larger, more diverse sample of women, including asymptomatic women.
“The next steps would be to get an ethnically diverse cohort of women prospectively collected and then see if these findings validate there, both findings about gestational age and the ones about preterm delivery,” she said. “Maybe, hopefully in the next five years, this might be available to the general public, if things validate.”
“It’s important to emphasize that this is a proof of principle, and it’s not a clinical test yet,” he said, adding that if it’s made available in the future, “it’s hard to tell right now” how much the blood test could cost, but it could be offered for around $100.
The state of preterm birth testing
Among the major differences between those two blood test studies are sample size and methodology, but their goals were the same: to predict preterm birth.
“As a neonatologist, we see many infants who are born preterm with little warning or known risk factors during the mother’s pregnancy,” said Dr. Noelle Younge, assistant professor of pediatrics at Duke University School of Medicine, who was not involved in the studies.
“The ability to noninvasively monitor fetal development and predict the risk of preterm birth through circulating markers could have a major impact on pregnancy monitoring and management,” she said. “These studies show that a lot of progress is being made. Further work is needed not only to understand how these tests perform in large studies but also to determine how they should be used clinically.”
After all, preterm birth is often unexpected and significantly increases an infant’s risk of long-term health and developmental problems, so new approaches to identify women at risk are needed, Younge said.
“Currently, diagnostic tools to predict the risk of preterm birth are limited,” she said. “There are blood tests in different stages of development, but none have been widely adopted in clinical practice. Continued work is needed to understand the utility and applications of these tests in prenatal care.”
The women had never given birth before and carried their pregnancies to 20 weeks or more between 2010 and 2014.
“The health and economic consequences of preterm birth are enormous, and it is understandable why physicians feel tremendous pressure to implement new practices to prevent preterm birth. However, that pressure does not eliminate the need to introduce new practices only when based on fully vetted evidence,” they wrote.
“Physician consensus committees should not legitimize new interventions until it is certain that those interventions will have clinical utility.”
News credit : Cnn