How a single blood sample could determine if you’re at risk of pre-eclampsia

The term “pre-eclampsia” is a worrying thing for any pregnant mother to hear, as it is a serious condition that can be dangerous for both mother and baby if left untreated.

The condition affects around one in 12 pregnancies, and is characterised by the combination of raised blood pressure (hypertension) and kidney or liver problems or protein in the urine. It can range from mild to severe, with mild cases affecting up to six per cent of pregnancies and rarer, more severe cases developing in about one to two per cent of pregnancies.

It is not known what causes pre-eclampsia, which usually develops during the second half of pregnancy (after 20 weeks) or soon after the baby is delivered. The early signs of pre-eclampsia are usually picked up during routine antenatal appointments and can be monitored and treated straight away.

According to pregnancy charity Tommy’s, most cases of pre-eclampsia are mild and have no effect on pregnancy. But if left untreated, the condition has the potential to progress to a more dangerous stage known as eclampsia. In worst case scenarios, this can lead to the death of the mother or baby.

“Women with pre-eclampsia may need to be admitted to hospital for treatment and monitoring,” the charity says. “Some women become unwell very quickly and need to have their baby delivered straight away. Others will need long stays in hospital so that they can be observed.”

However, researchers have found that a single blood sample can detect pregnant women who are risk of pre-eclampsia before the onset of any symptoms.

A study conducted by researchers from King’s College London (KCL) and Guys’ and St Thomas’ NHS Foundation Trust found that there are specific molecular profiles that can identify pregnancy complications, such as pre-eclampsia.

The study examined genetic material found in the blood samples of 2,500 women, from eight cohorts that included women from multiple ethnicities and nationalities, from different socioeconomic backgrounds and places.

Professor Rachel Tribe, from the Department of Women and Children’s Health at KCL, explained that the researchers used a “cutting-edge sequencing approach” to detect “cell free RNA (cfRNA)” in the blood of the pregnant women involved in the study.

After collecting the samples, the researchers analysed the cfRNA profiles, which are signals from the foetus and mother’s tissues, that reflect foetal development and healthy pregnancy progression.

They found that there are cfRNA signals that “deviate” from the signals of a healthy pregnancy, with a single blood sample able to reliably identify women at risk of developing pre-eclampsia months before any symptoms began.

Prof Tribe said: “Excitingly, this requires only a single blood sample and has potential to identify women at risk much earlier in pregnancy so that they can be more closely monitored and treated by the clinicians involved.”

The study, published in the Nature journal, was carried out in collaboration with pregnancy health platform Mirvie, which uses a blood test to detect complications before they occur. Machine learning was used to analyse tens of thousands of RNA messages from the mother, baby and placenta.

The Mirvie RNA platform can successfully identify 75 per cent of women who go on the develop the condition, which has made researchers hopeful that this test can be used more widely to investigate other pregnancy complications.

Prof Tribe explained that having a diverse group of women to draw samples from resulted in a “very reliable” molecular signature during the study, which has the “potential to outperform” other tests that are currently available.

“We are now focused on ongoing clinical research to further validate these results and improve the understanding of other pregnancy complications,” she added. “As a scientist, it was also extremely interesting to see that the molecular signature tells us something about the mechanisms associated with health in pregnancy and complications including pre-eclampsia; such knowledge will aid development of treatment strategies in the future.”

Marcus Green, CEO of Action on Pre-eclampsia, told The Independent: “This is a useful test which will work alongside current markers and we are impressed by these findings.

“The eventual role out will be very important and after further research this could be a welcome new tool. Anything that helps our understanding of pre-eclampsia is incredibly useful and the more tools available to clinicians to aid their work the better, after all our main concern is ensuing that women and babies come home from hospital safe and well.”