Randomized, Controlled Trial Using Low-Dose Aspirin in the Prevention of Preeclampsia in Women With Abnormal Uterine Artery Doppler at 23 Weeks Gestation

Abstract

In preeclampsia, the endothelial production of prostacyclin, a vasodilator and inhibitor of platelet aggregation, is reduced. At the same time, the production of thromboxane, a vasoconstrictor that promotes platelet aggregation, is increased. Aspirin can inhibit cyclooxygenase, which is important for the production of both of these substances, and a recent metaanalysis of 39 studies suggests that its prophylactic use is associated with a moderate reduction in the incidence of preeclampsia. This study evaluated low-dose aspirin as a preventive measure in women considered to be at high risk because of an abnormal uterine artery Doppler flow study. Color and pulsed Doppler screening studies estimated blood flow in the uterine arteries in 19,950 singleton pregnancies at 22 to 24 weeks gestation. More than 4% of women had a pulsatility index (PI) above 1.6 and were viewed as being at high risk of uteroplacental insufficiency. A total of 560 women at risk were randomly assigned to receive 150 mg aspirin or placebo daily up to 36 weeks gestation. The 2 groups were similar at baseline. No difference was found between the aspirin-treated women and the control group in the cumulative probability of preeclampsia across the range of gestational age. The respective incidence rates were 18% and 19%, and the rates for preeclampsia requiring delivery before 34 weeks gestation were 6% and 8%, respectively-not a significant difference. Aspirin also did not significantly alter the need for preterm delivery, the chance of a birth weight below the 5th percentile, or the risk of perinatal death or placental abruption. This multicenter randomized trial failed to show benefit from low-dose aspirin in pregnancies with impaired placentation. The risk of preeclampsia and the need for preterm delivery were not reduced.