A blood test predicts preeclampsia in pregnant women
The Food and Drug Administration has approved a blood test that can identify pregnant women who are at imminent risk of developing a severe form of high blood pressure called preeclampsia, one of the leading causes of disability and death in women of childbearing age.
The condition disproportionately affects black women in the United States and may have contributed to the recent death of Tori Bowie, a track and field athlete who won gold at the 2016 Olympics. Two of Ms Bowie’s black teammates – Allyson Felix and Tianna Bartoletta – also developed preeclampsia during their pregnancy.
The new test could provide an early warning, identifying which of the many pregnant women with symptoms will develop the life-threatening disease within the next two weeks.
“It’s groundbreaking. It’s revolutionary,” said Dr. Doug Woelkers, professor of maternal fetal medicine at the University of California, San Diego, on the test. “It’s the first advance in preeclampsia diagnostics since the 1900s, when the condition was first defined.”
However, to what extent the test improves outcomes and saves lives is not clear because there is no effective treatment for preeclampsia, which usually resolves after childbirth.
“We have no other therapy that reverses or cures preeclampsia other than delivering the baby, which is more of a last resort,” said Dr. Wolkers.
The new blood test from Thermo Fisher Scientific has been available in Europe for several years. It is aimed at pregnant women who are hospitalized for a blood pressure disorder between 23 and 35 weeks of pregnancy.
The test can say with an accuracy of up to 96 percent who will not develop preeclampsia within the next two weeks and can therefore be safely discharged from the hospital. However, two-thirds of women who get a positive result will develop severe preeclampsia during this time, and their babies may need to be delivered earlier.
Distinguishing between the two groups of women is a challenge that has long plagued physicians.
“The warning signs of preeclampsia are not very specific,” said Dr. Sarosh Rana, a professor of obstetrics and gynecology at the University of Chicago, who studied the test. “A lot of women have edema and headaches.” (Edema means swelling.)
“But we don’t really know who among those patients is at higher risk of really negative outcomes,” she said.
Preeclampsia affects about 1 in 25 pregnancies, and the incidence has been increasing in the United States in recent years. The problem usually begins around mid-pregnancy, but it can also occur after childbirth. A condition called eclampsia can develop, which can lead to seizures and death.
Black women in the United States have a far higher rate of preeclampsia than white women, and are three times more likely to have kidney damage or death from preeclampsia than white women. Black women are also more likely to lose their babies.
The blood test measures the ratio of two proteins produced by the placenta. A study published in November in the New England Journal of Medicine looked at 1,014 pregnant women hospitalized with hypertensive pregnancy disorder at 18 medical centers across the United States from 2019 to 2021. Just under a third were black and 16 percent Hispanic.
The researchers found that the two proteins in the blood of women who developed severe preeclampsia were severely imbalanced. Those with the highest ratios had a 65 percent chance of developing severe preeclampsia and delivering their child within two weeks, either spontaneously or by induction.
“If your levels are among the highest, deliver within a few days,” said Dr. Ravi Thadhani, an author of the study.
Women who have symptoms suggestive of preeclampsia but test negative can be reassured and sent home, but may need to have the test repeated every two weeks, Dr. Rana.
Preeclampsia develops quickly, and without a blood test, the warning signs can be vague.
“A woman can no longer feel well, be perfectly healthy, and have normal kidney and liver function, and within 24 to 48 hours these organs can fail and she develops brain swelling and seizures,” said Dr. Thadhani. “That’s the scary part of the disease.”