Effects of low-dose aspirin on uterine and fetal blood flow during pregnancy: results of a randomized, placebo-controlled, double-blind trial

Abstract

Objective: This study was conducted to evaluate uteroplacental and fetal hemodynamics in fetuses exposed to low-dose aspirin (100 mg/d).

Design: Randomized, placebo-controlled, double-blind trial.

Subjects: The study protocol included singleton pregnancies of less than 20 gestational weeks at risk for pre-eclampsia or fetal growth restriction. Exclusion criteria were diabetes mellitus, pre-existing proteinuric hypertension or fetal malformations. Forty-three pregnant women were randomly allocated to daily treatment with 100 mg aspirin (n = 22) or placebo (n = 21).

Methods: Pulsed Doppler measurements of the uterine artery, fetal middle cerebral artery, fetal aorta, ductus arteriosus and atrioventricular valves were performed longitudinally at 14 day intervals starting from 18 gestational weeks until delivery. Results were expressed as group medians (aspirin vs. placebo) and were analyzed by Mann-Whitney U-test.

Results: There was no difference in uterine, umbilical, aortic, middle cerebral and ductus arteriosus blood flow between the aspirin group and controls. Median ductal peak flow velocities increased with gestational age in both groups, but differences between groups did not reach significance. In the third trimester of pregnancy, ductal peak velocities > 140 cm/s were occasionally observed in both groups. However, end diastolic velocities > 35 cm/s or atrioventricular valve regurgitation never occurred.

Conclusions: Daily administration of low-dose aspirin during the second and third trimesters of pregnancy does not alter uteroplacental or fetoplacental hemodynamics and does not cause moderate or severe constriction of the ductus arteriosus.