THE EFFECT OF LOW-DOSE ASPIRIN ON UMBILICAL ARTERY DOPPLER MEASUREMENTS

OBJECTIVE: Our purpose was to determine if the maternal administration of low-dose (60 mg) aspirin from 24 weeks' gestation until delivery is associated with significant changes in longitudinal umbilical artery Doppler index values. STUDY DESIGN: Healthy, young nulliparous women with singleton gestations who were enrolled in a double-blind trial of low-dose aspirin for preeclampsia prevention underwent prerandomization and monthly postrandomization continuous-wave umbilical artery Doppler evaluations. The systolic-to-diastolic ratio and the resistance index were determined at each examination. Compliance with the medical regimen was assessed by pill counts and measurement of maternal serum thromboxane B2 levels. RESULTS: The prerandomization Doppler index values were similar between the two randomization groups in the 538 (aspirin 266, placebo 272) patients studied. We found no significant differences with univariate comparisons and multiple linear regression modeling in the postrandomization Doppler index values (p = 0.21 to 0.96). No differences were found when patients were assessed by randomization assignment group (intent to treat) or by biochemical evidence for compliance and absence of crossover with maternal serum thromboxane B2 levels. CONCLUSION: The use of low-dose aspirin from 24 weeks' gestation until delivery does not significantly affect umbilical artery Doppler index values.