Low-dose aspirin therapy improves fetal weight in umbilical placental insufficiency

A randomized, placebo-controlled, double-blind trial was carried out to evaluate the fetal benefits of low-dose aspirin (150 mg /day) as a treatment of placental insufficiency during the last trimester of pregnancy. Forty-six women referred for study because there was concern about fetal welfare were found to have an elevated umbilical artery wave form systolic /diastolic ratio. Mothers with severe hypertension were excluded because fetal condition would not necessarily be the dominant determinant of obstetric decision making. A distinction was made between a high systolic /diastolic ratio (>95th but <99.95th percentile) and an extreme systolic/ diastolic ratio (>99.95th percentile). There were 34 patients in the high ratio group and 12 in the extreme group. Aspirin therapy was associated with an increase in birth weight (mean difference 526 gm [p < 0.02]), head circumference (1.7 cm (p < 0.025]), and placental weight (136 gm (p < 0.02]) in those patients with a high initial umbilical artery systolic/ diastolic ratio. For the 12 women with an extreme initial systolic/ diastolic ratio, aspirin therapy did not result in a significantly different pregnancy outcome.