Low-Dose Aspirin During Pregnancy

Low-dose aspirin- also called baby aspirin- has been used in pregnancy for the last 40 years to, primarily, prevent or delay the onset of preeclampsia. Based on the findings from the US Preventive Services Task Force, low-dose aspirin therapy after 12 weeks of gestation modestly reduces the risk of preeclampsia in women with an increased risk. Numbers varied in different trials, but studies showed a 10-24% reduction rate of preeclampsia in women who took a daily low-dose aspirin. Aspirin is not usually recommended for use during pregnancy in high doses. However, research has shown that low-dose therapy is deemed safe with no increased risk for infant loss, fetal growth problems, fetal cognitive development, postpartum hemorrhage, or placental abruption.  

Therapy Standards

Low-dose aspirin therapy is recommended to start between 12-28 weeks gestation, ideally before 16 weeks, and continued daily until delivery. The normal dose recommended is 81mg/day. Because the main indication of aspirin therapy is to prevent or delay the onset of preeclampsia, the following are not recommended reasons to prescribe low-dose aspirin if preeclampsia is not present: unexplained stillbirth, reduce risk for fetal growth restriction, prevent spontaneous birth, and prevent early pregnancy loss. 

Indications for therapy

According to the US Preventive Services Task Force guidelines, women with one high risk factor or multiple moderate risk factors should be started on low-dose aspirin therapy. 

High risk factors:

• History of preeclampsia

• Multifetal pregnancy

• Chronic hypertension

• Type 1 or 2 diabetes

• Renal disease

• Autonomic disease

Moderate risk factors

• Nulliparity

• Obesity (BMI > 30)

• Family history of preeclampsia (mother or sister)

• Black or African American (due to social factors, not biological)

• Age of 35 or older, or younger than 18

• Personal history factors (e.g., low birthweight or small for gestational age, previous adverse pregnancy outcome, >10-year pregnancy interval)

• IVF pregnancy

Conclusion

The use of low-dose aspirin in pregnancy has greatly improved outcomes for at risk mothers for preeclampsia. Starting therapy as early as 12 weeks gestation has been shown in studies to prevent or delay the onset of preeclampsia.

Sources

Low-dose aspirin use during pregnancy. American College of Obstetricians and Gynecologists. (2018, July). https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2018/07/low-dose-aspirin-use-during-pregnancy 

Preeclampsia Foundation. (2023, August 3). Preeclampsia - prenatal aspirin. Prenatal Aspirin. https://www.preeclampsia.org/prenatal-aspirin 

Assessed and Endorsed by the MedReport Medical Review Board