Expert guidelines that clinicians across the country use to assess the risk of preeclampsia in pregnant women may be ineffective.
The recommendations designed by the U.S. Preventive Services Task Force do not accurately predict risk of developing the condition and lead to nonspecific treatment guidance for the majority of patients, researchers found in a study published Thursday in JAMA Network Open. The findings have implications for reforming risk guidelines and increasing personalized care.
“This is a valuable, descriptive study,” Molly McAdow, a maternal-fetal medicine specialist at Yale New Haven Hospital, said. “There is certainly an opportunity for us to do better with a more stringent screening test.”
Screening for preeclampsia risk is essential, given that the disease can cause high blood pressure, organ damage, and even maternal and fetal death. But also crucial is that screening guidelines accurately assess a patient’s risk of developing the condition, instead of broadly prescribing preventative treatments like baby aspirin. In the U.S., preeclampsia affects about 4% of all pregnancies, and disproportionately impacts non-hispanic Black women.
USPSTF’s recommendations, which are in line with those from the American College of Obstetricians and Gynecologists, designate patients into high, moderate, and low risk categories. The guidelines recommend low-dose aspirin if a patient has at least one high-risk factor, such as a history of preeclampsia and pregestational diabetes, or at least two moderate risk factors, including obesity and age.
“The Task Force’s rigorous review of all the latest high-quality research clearly shows that taking aspirin helps women at high risk prevent preeclampsia, improving their health and the health of their babies,” USPSTF chair Michael Silverstein told STAT “Fundamentally, one of the best ways to help address the maternal mortality crisis is to ensure that everyone who is pregnant is able to access the preventive services that have been proven to help save their lives.”
More on preeclampsia
To assess the utility of the guidelines, the researchers employed an observational cohort study. They enrolled over 5,600 patients with singleton pregnancies at 11 academic medical centers across the country between July 2020 and March 2023. The study was funded by Mirvie, a company developing a blood test for preeclampsia.
Under the USPSTF recommendations, 89 percent of the population is classified as at risk for preeclampsia, with over 70 percent at moderate risk, the study found. But the researchers established that just 10.5 percent and 23.5 percent of moderate and high risk patients, respectively, actually developed the condition. That means that the guidelines have a very high false positive screening rate, McAdow said.
“If the intended utility of the guidelines is to facilitate the focus of clinical attention and limited clinical resources on those at greatest risk of preeclampsia, identifying the majority of the population as at risk does not meet this end,” study authors said in the paper.
The researchers also found that the association of moderate risk factors with preeclampsia was inconsistent, with the exception of never having given birth. This suggests that the factors don’t necessarily portend higher risk of the condition, according to Cynthia Gyamfi-Bannerman, a study co-author and maternal-fetal medicine specialist at UC San Diego Health.
Of particular note is that maternal race — one of USPSTF’s moderate risk factors — was not correlated with preeclampsia, which is contrary to existing clinical practices. This implies that structural inequities, not race itself, is what underlies the condition.
The study also reported that aspirin is underprescribed in patients who are classified as being at moderate risk. For those with two or more moderate risk factors, the rate of aspirin prophylaxis is 50.4 percent. For those with one factor, it’s just 23.8 percent. This suggests that the USPSTF guidelines provide little utility for aspirin use among individuals at moderate risk, the study’s authors argue.
And the percentage of patients who actually used the medication is likely significantly lower, according to Thomas McElrath, a study co-author and OB-GYN at Brigham and Women’s Hospital. For the study, only data on the number of patients prescribed aspirin was available. However, previous research has shown that fewer than fifty percent of patients who were prescribed the medication actually take it.
McElrath hypothesized that this difference could be due to such a high proportion of individuals being classified as at risk for the condition. Patients don’t like the idea of having to take something just because they meet a certain criteria.
“A lot of times, people wanted it to be a little bit more personalized,” McElrath said.
The study has a few limitations. One is that a large percentage of patients in the high-risk category likely took aspirin, according to McAdow, thereby impacting the proportion of patients in the subgroup who went on to develop preeclampsia. This makes it difficult to interpret test statistics like sensitivity and specificity.
The study also excluded multigestational pregnancies and pregnancies conceived through in vitro fertilization, two significant risk factors for preeclampsia, McAdow said. And it had an overrepresentation of high-risk pregnancies, given that the researchers enrolled patients at academic medical centers, which often treat individuals with more complicated cases.
Still, McAdow agrees with the paper’s conclusion about the need for better guidelines for preeclampsia screening. Treatment for the disease a hundred years ago looks “remarkably similar” to treatment today, according to McElrath.
“There’s almost no other field in medicine where the pattern of diagnosis and therapy and risk determination is that old,” he said. “That’s hopefully, optimistically, starting to change.”
