Low-dose aspirin for prevention of adverse outcomes related to abnormal placentation.

Meta-analysis of randomized studies on the use of low-dose aspirin in women at high risk of preeclampsia (PE) has demonstrated that if treatment is initiated at ≤16 weeks' gestation, there is significant reduction in the risk of PE [relative risk (RR) 0.47, 95% confidence interval (CI) 0.36-0.62], fetal growth restriction (RR 0.46, 95% CI 0.33-0.64), preterm birth (RR 0.35, 95% CI 0.22-0.57) and perinatal death (RR 0.41, 95% CI 0.19-0.92), whereas the effect of treatment after 16 weeks is substantially less (RR 0.78, 95% CI 0.61-0.99; RR 0.98, 95% CI 0.88-1.08; RR 0.90, 95% CI 0.83-0.97; and RR 0.93, 95% CI 0.73-1.19, respectively). Moreover, the decrease in the risk of PE from early onset treatment seems to be related to the dose of aspirin, and a dose of >80 mg daily should be considered for optimal benefits.