Objective To determine the effectiveness of low dose aspirin in women at high risk of adverse outcomes associated with pre-eclampsia.
Design A collaborative randomised trial comparing the effects of low dose aspirin (60 mg) with placebo on pre-eclampsia and other materno-fetal complications associated with hypertension.
Setting Twelve teaching maternity hospitals and 182 obstetricians' offices in Brazil.
Subjects One thousand and nine women considered to be at high risk for the development of pre-eclampsia, or its complications, entered the study between 12 and 32 weeks of gestation. They were randomly allocated to receive aspirin (498 women) or placebo (511 women) until delivery, and follow up was obtained for 96%.
Results There were no significant differences between the treatment groups in the incidence of proteinuric pre-eclampsia (6.7% aspirin-allocated compared with 6–0% placebo-allocated women), of preterm delivery (22.3% compared with 26.1%), of intrauterine growth retardation (8.5% compared with 10.1%), or of stillbirth and neonatal death (7.3% compared with 6.0%), nor were there significant differences in the incidence of proteinuric pre-eclampsia in any subgroup of women studied, including those who had systolic blood pressures of 120 mmHg or above at entry (8.5% compared with 7.3%) or those who were chronically hypertensive (10.0% compared with 7.1%). Aspirin was not associated with a significant excess of maternal or fetal bleeding.
Conclusion The results of this study do not support the routine prophylactic administration of low dose aspirin in pregnancy to any category of high risk women (even those who have chronic hypertension or who are considered to be especially liable to early onset pre-eclampsia).