Based on its review of the available evidence, the task force recommends the use of low-dose aspirin (defined as 81 mg/day) as preventive medication after 12 weeks’ gestation in people who are at high risk for preeclampsia. This is a grade "B” recommendation, and applies to asymptomatic pregnant people who are at high risk for preeclampsia and who have had no prior adverse events with or contraindications to low-dose aspirin.
Preeclampsia occurs in about 4% of pregnancies in the United States and can contribute to a number of negative outcomes for both the mother and baby, including preterm birth, organ damage and death. Those at increased risk for the condition include (but are not limited to) people
“Fortunately, clinicians can help high-risk pregnant people and their babies stay healthy through daily low-dose aspirin to prevent preeclampsia,” task force member Aaron Caughey, M.D., M.P.P., M.P.H., Ph.D., said in a press release. “It’s important for clinicians to take into account a number of health factors that increase preeclampsia risk when determining whether to recommend low-dose aspirin.”
The final recommendation statement is consistent with the task force’s September 2014 recommendation on the topic, which also recommended low-dose aspirin as a preventive medication after 12 weeks of gestation in women at high risk for preeclampsia.
The AAFP supported the 2014 recommendation.
To update the existing recommendation, the USPSTF commissioned a systematic review to evaluate the effectiveness of low-dose aspirin use to prevent preeclampsia. The review consisted of relevant studies published between January 2013 and May 15, 2020, and included evidence on the effectiveness of low-dose aspirin in preventing preeclampsia in pregnant people at increased risk and in decreasing adverse maternal and perinatal health outcomes. It also examined the maternal and fetal harms of low-dose aspirin use during pregnancy. A total of 23 studies were included in the review, 19 of which were carried forward from the task force’s previous evidence review conducted in 2014.
Evidence suggested that low-dose aspirin use was effective in reducing the risks of a number of adverse health outcomes. A pooled relative risk analysis of results from several trials found that in individuals at increased risk for preeclampsia, low-dose aspirin use reduced the risks of preterm birth, small for gestational age/intrauterine growth restriction, perinatal mortality and fetal intracranial bleeding.
In addition, analysis of the trial results did not show evidence of harms from daily low-dose aspirin use during pregnancy. Bleeding harms were uncommon, and pooled results were not statistically significant for placental abruption, postpartum hemorrhage or intracranial bleeding. The task force also did not find a difference in harms based on aspirin dosage, timing of aspirin initiation or for specific populations based on limited subgroup comparisons.
The research team also noted several evidence gaps. They called for additional studies in a number of areas, including research that would
The task force also called specifically for additional research on aspirin use in populations that have the highest rates of preeclampsia, including Black people. Of the trials included in the evidence review, only three enrolled substantial numbers of Black and Latinx study participants, and none of the trials enrolled significant numbers of other minority racial or ethnic groups, which made it difficult for the task force to assess whether there could be racial or ethnic differences in the effectiveness or potential harms of aspirin use in pregnancy.
Given the limited evidence available for review, the task force stated that future trials should recruit adequate numbers of people from varying racial and ethnic populations so they are sufficiently powered to determine the effectiveness of different aspirin dosages and timing of initiation in the populations that bear the greatest disease burden.
“Black people are more likely to develop preeclampsia and experience serious complications from it than people of other races due to a variety of social and health inequities,” noted Michael Silverstein, M.D., M.P.H., a member of the USPSTF. “The task force is committed to addressing these inequities, and we are calling for more research on how to best prevent preeclampsia in Black people who are pregnant so that this disparity can be addressed in the health community.”
A draft recommendation statement was posted to the USPSTF website from Feb. 23 to March 22, 2021.
In response to requests for an explicit acknowledgement of the role of systemic racism in the prevalence of and mortality from preeclampsia, the task force added specific language on disparities in prevalence, mortality and risk factors to the Importance section of the recommendation statement.
A number of commenters asked for clarification of risk factors. In response, the task force revised both a table on the clinical risk assessment for preeclampsia and language in the Implementation section.
The USPSTF also added language to the Implementation section in response to a question about the harms of aspirin, and added clarifying language to the Practice Considerations section.
The AAFP’s Commission on Health of the Public and Science will review the task force’s final recommendation statement, final evidence summary and evidence review, and will then determine the Academy’s stance on the recommendation, up to and including a revision of the Academy’s current recommendation.
Once the review is completed, members can visit the clinical preventive services recommendations section of aafp.org for the latest recommendations.