Blood Tests Predict Pre-eclampsia in Pregnant Women

The Food and Drug Administration has approved a blood test that can identify pregnant women at risk of developing a severe high blood pressure called pre-eclampsia, a leading cause of disability and death among women who give birth to children.

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 star who won gold at the 2016 Olympics. Two of Ms. Bowie—Allyson Felix and Tianna Bartoletta—also had pre-eclampsia during their pregnancies.

The new test may offer an early warning, identifying which of the many pregnant women who have symptoms suggestive of developing the life-threatening illness in the next two weeks.

“This is a breakthrough. This is revolutionary,” said Dr. Doug Woelkers, a professor of maternal fetal medicine at the University of California, San Diego, about the test. “This is the first step forward in the diagnosis of pre-eclampsia since 1900, when the condition was first defined.”

To what extent this test will improve outcomes and save lives is unclear, as there is no effective treatment for pre-eclampsia, which usually subsides after birth.

“We don't have a therapy that reverses or cures pre-eclampsia other than delivering the baby, which is more like a last resort,” says Dr. Woelkers.

The new blood test, made by Thermo Fisher Scientific, has been available in Europe for several years. It is intended for pregnant women who are hospitalized for blood pressure disorders at 23 to 35 weeks of gestation.

The test can tell, with up to 96 percent accuracy, who will not develop pre-eclampsia in the next two weeks and can be safely discharged from the hospital. Conversely, two-thirds of women who have a positive result will develop severe preeclampsia by this time, and their baby may need to be delivered early.

Differentiating between the two groups of women is a challenge that has long vexed doctors.

“Warning signs of pre-eclampsia are not very specific,” says Dr. Sarosh Rana, a professor of obstetrics and gynecology at the University of Chicago who has studied the test. “A lot of women will have edema and headaches.” (Edema means swelling.)

“But we don't really know which of the patients is at higher risk for very poor outcomes,” he said.

Pre-eclampsia affects about one in 25 pregnancies, and its incidence has increased in recent years in the United States. The problem usually starts around mid-pregnancy, although it can occur after delivery. This can lead to a condition called eclampsia, which can lead to seizures and death.

Black women in the United States have much higher rates of pre-eclampsia than white women, and they are three times more likely to suffer kidney damage or die from pre-eclampsia than white women. Black women are also more likely to lose their babies.

The blood test measures the ratio of the two proteins produced by the placenta. A study published in NEJM Evidence in November tracked 1,014 pregnant women who were hospitalized with hypertensive disorder of pregnancy at 18 medical centers in the United States from 2019 to 2021. Less than a third were black, and 16 percent were Hispanic.

The researchers found that the two proteins were grossly imbalanced in the blood women with severe pre-eclampsia. Those with the widest ratio had a 65 percent chance of developing severe pre-eclampsia and delivering their baby within two weeks, either spontaneously or by induction.

“If your levels are among the highest, you give birth within a few days,” says Dr. Ravi Thadhani, author of the study.

Women who have symptoms suggestive of pre-eclampsia but test negative can be reassured and sent home, but they may need to be retested every two weeks, said Dr. shutter.

Pre-eclampsia progresses quickly, and without a blood test, the warning signs can be unclear.

“A woman can go from feeling fine and being completely healthy and having normal kidney and liver function, and within 24 to 48 hours those organs can fail and she has brain swelling and seizures,” says Dr. Thadhani. “That's the scary part of this disease.”