Blood test predicts increased risk of developing pre-eclampsia

A blood test taken in the first trimester of pregnancy to measure cell-free DNA methylation can help to predict the risk of preterm pre-eclampsia.

Pre-eclampsia is a serious pregnancy complication that can lead to an increased risk of stillbirth, maternal organ damage, seizures, and death, but treatment, such as taking low dose aspirin, started in the first trimester of pregnancy can prevent harm. Researchers at KU Leuven, Belgium, have developed an epigenomic test to help clinicians identify at-risk patients before symptoms develop.

'We don't see it as something that should be applied independent of all the other tests, but more as an add-on,' Dr Bernard Thienpont, lead author on the study published in Nature Medicine, told LiveScience.

When cells die and are broken down, small fragments of DNA end up in the bloodstream: this is called cell-free DNA (cfDNA). In pregnancy, some of the DNA in the mother's bloodstream comes from the fetus and placenta, and this is used in noninvasive prenatal testing for conditions such as Down's syndrome.

Pre-eclampsia is linked to poor blood flow and low oxygen levels in the placenta, causing the mother's blood pressure to rise to compensate. Research on other tissues has shown that oxygen deprivation is associated with certain epigenetic changes, specifically to the DNA methylation that affects gene expression.

Because some of the cfDNA comes from the placenta, the researchers hoped that it could be used to look for these methylation patterns, that could be indicative of early pre-eclampsia. They measured DNA methylation levels in the blood of 498 pregnant women at 12 weeks gestation, one-third of whom went on to develop early pre-eclampsia.

They found that the women who developed pre-eclampsia had different patterns of methylation in cfDNA from the placenta than those who did not. They used these differences to create a model to predict which women are likely to develop pre-eclampsia. The model alone identified 38 percent of these, but once clinical and demographic factors were included, this increased to 57 percent, with very few false positives. This is compared to 30 percent of cases that were correctly predicted based on maternal risk factors alone.

'The implications are exciting; the technology may provide a non-invasive means to profile the placental methylome in vivo to glean insights into placental biology,' wrote Professor Tu'uhevaha Kaitu'u-Lino and colleagues from the department of obstetrics and gynaecology at the University of Melbourne, Australia, who authored a comment piece about the findings, also published in Nature Medicine.