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.
Pregnancy resulting from fertility therapy
Current ACOG and USPSTF guidelines do not specifically identify pregnancies resulting from assisted reproductive technology as a major or moderate risk factor for preeclampsia.2,3 In a study comparing 83,582 births resulting from in vitro fertilization (IVF) and 1,382,311 births to fertile women, treatment with autologous cryopreserved embryos (adjusted odds ratio [aOR], 1.30), fresh donor embryos (aOR, 1.92), and cryopreserved donor embryos (aOR, 1.70) significantly increased the risk of preeclampsia.13 However, use of fresh autologous embryos did not increase the risk of preeclampsia (aOR, 1.04). These associations persisted after controlling for diabetes, hypertension, body mass index, and cause of infertility.13
Other studies also have reported that use of cryopreserved embryos is associated with a higher rate of preeclampsia than use of fresh autologous embryos. In a study of 825 infertile women undergoing IVF and randomly assigned to single embryo cryopreserved or fresh cycles, the rate of preeclampsia was 3.1% and 1.0% in the pregnancies that resulted from cryopreserved versus fresh cycles.14
What is the optimal dose of aspirin?
ACOG and the USPSTF recommend aspirin 81 mg daily for the prevention of preeclampsia.2,3 The International Federation of Gynecology and Obstetrics (FIGO) recommends aspirin 150 mg daily for the prevention of preeclampsia.15 The FIGO recommendation is based, in part, on the results of a large international clinical trial that randomly assigned 1,776 women at high risk for preeclampsia as determined by clinical factors plus biomarker and ultrasound screening to receive aspirin 150 mg daily or placebo daily initiated at 11 to 14 weeks’ gestation and continued until 36 weeks’ gestation.16 Preeclampsia before 37 weeks’ gestation occurred in 4.3% and 1.6% of women in the placebo and aspirin groups (OR, 0.38; 95% CI, 0.20–0.74; P = .004).16 FIGO recommends that women at risk for preeclampsia with a body mass <40 kg take aspirin 100 mg daily and women with a body mass ≥40 kg take aspirin at a dose of 150 mg daily. For women who live in a country where aspirin is not available in a pill containing 150 mg, FIGO recommends taking two 81 mg tablets.15 FIGO recommends initiating aspirin between 11 and 14 weeks and 6 days of gestation and continuing aspirin therapy until 36 weeks of gestation.15
Aspirin is an inexpensive intervention with many possible benefits
For many nulliparous women and some parous women aspirin treatment initiated early in pregnancy will improve maternal and newborn outcomes, including reducing the risk of preeclampsia, preterm birth, and intrauterine growth restriction.1 Obstetricians may want to begin to expand the indications for offering aspirin to prevent preeclampsia from those recommended by ACOG and the USPSTF to include nulliparous women with a booking systolic pressure of 120 to 134 mm Hg and women whose pregnancy was the result of an assisted reproduction treatment that used cryopreserved embryos. In addition, obstetricians who currently prescribe 81 mg of aspirin daily might want to consider increasing the prescribed dose to 162 mg of aspirin daily (two 81 mg tablets daily or one-half of a 325 mg tablet). Aspirin costs about less than 5 cents per 81 mg tablet (according to GoodRx website). It is an inexpensive intervention that could benefit many mothers and newborns. ●
