Aspirin Use for the Prevention of Preeclampsia, an Evidence-Based Review

Preeclampsia is a multisystem hypertensive disorder of pregnancy that is defined by new-onset hypertension after 20 weeks of gestation along with proteinuria or evidence of end-organ dysfunction. Affecting 2-8% of pregnancies worldwide, preeclampsia remains a leading cause of maternal and perinatal morbidity and mortality. This disorder originates secondary to defective placentation during the first trimester, causing incomplete remodeling of the uterine spiral arteries, resulting in placental hypoperfusion, oxidative stress, and the release of anti-angiogenic factors into the maternal circulation. This pathophysiology provided researchers a rationale for the use of low-dose aspirin as a preventive strategy for preeclampsia. Early studies investigated low-dose aspirin initiated at variable gestational ages and failed to show significant reductions in the incidence of preeclampsia. However, over the years, multiple meta-analyses studying aspirin use for preeclampsia prevention revealed a consistent decrease in the incidence of preeclampsia with the use of low-dose aspirin initiated at or before 16 weeks of gestation, with the efficacy being largely dependent on the time of initiation. In 2017, a randomized controlled trial demonstrated a statistically and clinically significant reduction in the incidence of preeclampsia leading to preterm delivery with aspirin initiated before 16 weeks gestation in women identified as high risk by first-trimester algorithm-based screening. Based on the strong evidence in support of aspirin use for preeclampsia prevention, current guidelines recommend initiation of aspirin 81 mg after 12 weeks and ideally before 16 weeks for all pregnant women at increased risk for preeclampsia.