Randomized controlled trial using low-dose aspirin in the prevention of pre-eclampsia in women with abnormal uterine artery Doppler at 23 weeks' gestation.

OBJECTIVE Pre-eclampsia, which is a major cause of perinatal and maternal morbidity and mortality, is thought to be due to impaired perfusion of the placenta. There is contradictory evidence that the administration of low-dose aspirin may provide effective prophylaxis against the subsequent development of pre-eclampsia. In this study we tested the hypothesis that in women identified as being at high-risk for pre-eclampsia, because of impaired flow in the uterine arteries, the prophylactic use of low-dose aspirin from 23 weeks of gestation can reduce the incidence of pre-eclampsia. METHODS We used color and pulsed Doppler to measure the flow in the uterine arteries in 19,950 singleton pregnancies at 22-24 weeks of gestation. Those women exhibiting increased impedance were recruited into a randomized study of aspirin 150 mg per day or placebo. We compared the two groups for the incidence of pre-eclampsia and the other consequences of impaired placentation. RESULTS The screening study identified 844 women (4.2%) as being at high risk of uteroplacental insufficiency. After exclusion and refusal, 560 women were randomly allocated to aspirin 150 mg or placebo per day until 36 weeks' gestation. There were no significant differences between the aspirin and placebo groups in either the incidence of pre-eclampsia (18% vs. 19%, P = 0.6) or pre-eclampsia requiring delivery below 34 weeks (6% vs. 8%, P = 0.36). Furthermore, the administration of aspirin did not significantly alter the incidence of preterm delivery (24% vs. 27%, P = 0.46), birth weight below the 5th centile (22% vs. 24%, P = 0.4), perinatal death (3% vs. 1%, P = 0.33) or placental abruption (4% vs. 2%, P = 0.12). CONCLUSION In pregnancies with impaired placentation, as demonstrated by increased impedance to flow in the uterine arteries, the daily administration of 150 mg aspirin after 23 weeks of gestation does not prevent the subsequent development of pre-eclampsia.