Preeclampsia, a pregnancy complication characterized by high blood pressure and high protein levels in urine, affects five to seven percent of pregnancies and causes more than 70,000 maternal deaths and 500,000 fetal deaths worldwide each year (1). 

Currently, doctors rely on a mix of clinical and demographic factors to assess the risk of preeclampsia, but these are not always reliable and often result in high-risk individuals being overlooked (2).

Now, the biotechnology company Mirvie has developed an at-home blood test based on RNA in maternal blood that predicts who is likely to develop preeclampsia months before symptoms begin.

“This test gives us a window of opportunity where we can instigate a preventive action plan that can help reduce or delay the onset of preeclampsia and improve outcomes,” said Carrie Haverty, a study coauthor and Vice President of Product Management at Mirvie.

Prevention of preeclampsia is important not only for the health of the mother and baby during pregnancy, but also for the mother’s long-term health. “Preeclampsia survivors have long-term cardiovascular disease risk that's equivalent to that of being a smoker,” Haverty said (3).

In a study published in Nature Communications, the team analyzed blood samples from more than 9,000 pregnant women during their second trimester (4). By looking at RNA fragments circulating in maternal blood, they obtained information about maternal gene expression on which the scientists could base their predictions.

They discovered that a specific placental gene, called PAPPA2, was overexpressed in women who later developed severe preeclampsia and had early delivery, even if they had no known traditional risk factors. The researchers also found a link between specific immune-related genes, such as CD163, and milder cases of preeclampsia.

Unlike other medical conditions, we have not had any kind of precision medicine and predictive care around preeclampsia at all.
- Carrie Haverty, Mirvie

To turn their findings into a useful tool, the team created a blood test — called the Encompass test — based on a panel of placental and immune-related genes. When validated in women aged 35 and older without pre-existing high-risk conditions, and who were between 18 and 22 weeks pregnant, the test identified 91 percent of pregnancies that developed preterm preeclampsia, months before symptoms arose. The test also ruled out those who are not at risk with over 99 percent accuracy.

“Unlike other medical conditions, we have not had any kind of precision medicine and predictive care around preeclampsia at all,” said Haverty. “This is such a potential game changer.”

Lina Bergman, an obstetrician and preeclampsia researcher at the University of Gothenburg who was not involved in the study, called the work “an important contribution to the field” and said that it highlights how “preeclampsia is a heterogeneous disorder” with different subtypes.

Bergman applauded the authors for including external validation, “because it's much more robust data than just developing an algorithm in one population.” However, she cautioned that preventive care before the second trimester is ideal, and that “these markers need to be confirmed in the first trimester of pregnancy.” She also emphasized the importance of testing in diverse global populations, noting that predictive biomarkers “can behave a bit differently in different populations.”

On a practical note, “these tests cost a bit of money and need to be translated to a more affordable technique to be incorporated into the clinical routine,” she said.

Bergman added that while advanced tests like this one are valuable, basic antenatal care — which “is one of the most important pillars to reduce maternal mortality and morbidity” — is still lacking in many low- and middle-income countries, as well as in maternity care deserts in the United States. “We also need to direct research funds and efforts into building sustainable antenatal care programs globally,” she said.

Currently, the Encompass test is commercially available in the US, and Mirvie is assessing expansion plans globally.

References

1. Dawson, E.L. Preeclampsia, Genomics and Public Health. CDC: Genomics and Precision Health Blog – Archive. (2022).
2. Krishnamurti, T. et al.  Use of a Smartphone App to Explore Potential Underuse of Prophylactic Aspirin for Preeclampsia. JAMA Netw Open  4, e2130804 (2021).
3. Chen, C.W. et al.  Pre-eclampsia and cardiovascular disease. Cardiovasc Res  101, 579–586 (2014).
4. Elovitz, M.A. et al.  Molecular subtyping of hypertensive disorders of pregnancy. Nat Commun  16, 2948 (2025).