Despite Guidelines, Aspirin Is Used in Fewer Than One in Four High-risk Pregnancies

NEW ORLEANS, LA—Less than a quarter of people at high risk for preeclampsia, the leading cause of maternal morbidity and mortality, use aspirin as a protective measure during pregnancy, according to observational data from Mass General Brigham.  

Preeclampsia affects up to 7% of pregnancies and is known to up CVD risks both in the months after pregnancy and later in life. Low-dose aspirin has been recommended by US Preventive Services Task Force (USPSTF) guidelines since 2014 to prevent this complication in women at high-risk.

“For only 25% of high-risk individuals to get [aspirin] is pretty shocking and disappointing,” lead researcher Emma Lee, BA (Harvard Medical School, Boston, MA), told TCTMD.  She said the data, culled from electronic health records (EHR) and presented this past weekend at the American College of Cardiology 2026 Scientific Session, demonstrates pitiful adherence to guidelines.

Senior author Emily S. Lau, MD, MPH (Mass General Brigham, Boston, MA), called the findings “striking and sobering.” She told TCTMD that there are likely many drivers at play, including failures by physicians who should be prescribing the medication, the patient’s ability to adhere, and other social and economic factors. At the end of the day, “this probably highlights, certainly on the provider side, that we’re not doing a good enough job ensuring that we’re applying this recommendation universally,” she said.

Lau urged physicians to “do better,” but stressed that this is a broader problem. “This is a systems issue,” she said. “We are seeing all of these risk factors that should be associated strongly with aspirin use, . . and yet we are seeing that many of these women, for example, with autoimmune disease, renal disease, are essentially not likely to get aspirin [compared with] their otherwise healthy counterparts.”

She called for widespread efforts to ensure that all patients who may benefit from aspirin receive it. “We can’t leave it to chance,” Lau argued.

Low Rates of Use

For the study, researchers looked at EHR data from 21,326 women (30,767 pregnancies) who delivered at Mass General Brigham between 2013 and 2023. Half of all pregnancies were deemed to be at high risk for preeclampsia, defined as the presence of at least one high-risk factor (history of preeclampsia, multifetal gestation, chronic hypertension, diabetes, renal disease, or autoimmune disease) or two moderate-risk factors (nulliparity, obesity, Black race, low socioeconomic status, age ≥ 35 years, or prior adverse pregnancy outcome).

They used a very broad definition of aspirin use, which was at least one mention of the drug in the EHR between 0 and 28 weeks gestation.

Before the USPSTF recommendation took effect, aspirin use was identified in only about 3-4% of high-risk pregnancies. This proportion increased steadily to 10% in 2018, when the American College of Obstetrics and Gynecology formally endorsed aspirin use in these individuals. While the rate continued to grow in the years to follow, it only reached 24% by 2023.

On multivariate analysis, the risk factors that were most associated with aspirin use were history of preeclampsia, multifetal gestation, diabetes, and hypertension. Notably, both renal disease and autoimmune disease were less likely to be associated with aspirin use than the other high-risk factors.

Because of how aspirin use was defined in the study, it’s likely that consistent aspirin use was even less common, according to Lee. “That record can either be aspirin formally coded as a medication in the EHR or also it could be a text-based search in a note,” she clarified, adding that the findings are “undercounting people who are actually taking aspirin across the course of their pregnancy.”

Moving the Needle

Ultimately, “aspirin is a pretty accessible, low-cost, low-risk medication that has been scientifically proven to prevent preeclampsia in these patients,” Lee said.

Lau acknowledged that many women who stand to benefit from aspirin might have trouble taking a medication for a variety of reasons, including perception of risk. “While these patients are high-risk, . . . these women consider themselves to be very healthy,” she said. “Trying to recommend a once-a-day medication during pregnancy is always a challenge.”

Going forward, Lee said she’d like to investigate further the drivers of the lackluster aspirin use in this population. Lau agreed, adding that she’d like to eventually build interventions to fix the problem.

“That’s where I think we want this work to move toward, she said. “How can we develop interventions, maybe first in our own system and then widely disseminated, to really move the needle here? We’ve got a long way to go to get from a quarter to a hundred percent, but I do think that there’s now an opportunity for us.”