Prescribing aspirin to improve pregnancy outcomes: Expand the indications? Increase the dose?
Low-dose aspirin is effective in reducing the risk of developing preeclampsia. Questions remain about who should be treated and the optimal aspirin dose.
Booking systolic blood pressure, 120 to 134 mm Hg
All obstetricians recognize that women with chronic hypertension should be treated with low-dose aspirin because they are at high risk for preeclampsia. However, there is evidence that nulliparous women with a booking systolic pressure ≥120 mm Hg might also benefit from low-dose aspirin treatment. In one US trial, 3,135 nulliparous normotensive women (booking blood pressure [BP] <135/85 mm Hg) were randomly assigned to treatment with aspirin (60 mg daily) or placebo initiated between 13 and 26 weeks’ gestation. Preeclampsia occurred in 6.3% and 4.6% of the women treated with placebo or aspirin, respectively (RR, 0.7; 95% CI, 0.6–1.0; P = .05).9 A secondary analysis showed that, among 519 nulliparous women with a booking systolic BP from 120 to 134 mm Hg, compared with placebo, low-dose aspirin treatment reduced the rate of preeclampsia from 11.9% to 5.6%.9 Aspirin did not reduce the rate of preeclampsia among nulliparous women with a booking systolic BP <120 mm Hg.9 A systematic review of risk factors for developing preeclampsia reported that a booking diastolic BP of ≥80 mm Hg was associated with an increased risk of developing preeclampsia (RR, 1.38).10
The American Heart Association (AHA) and the American College of Cardiology (ACC) recently updated the definition of hypertension.11 Normal BP is now defined as a systolic pressure <120 mm Hg and diastolic pressure <80 mm Hg. Elevated BP is a systolic pressure of 120 to 129 mm Hg and diastolic pressure of <80 mm Hg. Stage I hypertension is a systolic BP from 130 to 139 mm Hg or diastolic blood pressure from 80 to 89 mm Hg. Stage II hypertension is a systolic BP of ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg.11
A recent study reported that 90% of women at 12 weeks’ gestation have a BP of ≤130 mm Hg systolic and ≤80 mm Hg diastolic, suggesting that the AHA-ACC criteria for stage I hypertension are reasonable.12 Obstetricians have not yet fully adopted the AHA-ACC criteria for defining stage I hypertension in pregnant women. Future research may demonstrate that a booking systolic BP
≥130 mm Hg or a diastolic BP ≥80 mm Hg are major risk factors for developing preeclampsia and warrant treatment with low-dose aspirin.
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