What is the role of aspirin (acetylsalicylic acid) as prophylaxis in pregnancy?

Role of Low-Dose Aspirin as Prophylaxis in Pregnancy

Low-dose aspirin (81 mg/day) is strongly recommended as preventive medication after 12 weeks of gestation in women who are at high risk for preeclampsia and should be continued until delivery. 1

Indications for Low-Dose Aspirin Prophylaxis

High-Risk Factors (Any one factor qualifies for aspirin prophylaxis):

• History of preeclampsia, especially early-onset preeclampsia with delivery <34 weeks 2, 3
• Multifetal gestation 2, 3
• Chronic hypertension 2, 3
• Type 1 or type 2 diabetes 2, 3
• Renal disease 2, 3
• Autoimmune disease (such as systemic lupus erythematosus or antiphospholipid syndrome) 2, 3

Moderate-Risk Factors (More than one factor qualifies for aspirin prophylaxis):

• First pregnancy (nulliparity) 3, 4
• Maternal age ≥35 years 3, 4
• BMI >30 kg/m² 3, 4
• Family history of preeclampsia (mother or sister) 3, 4
• Sociodemographic characteristics (low socioeconomic status) 3, 4

Dosage and Timing

• Dosage: 81 mg/day is the standard recommended dose in the United States 1, 5
• Special populations: Women with diabetes may benefit from higher doses (100-150 mg/day) 2
• Initiation: Start between 12-16 weeks of gestation for optimal effect 1, 5, 3
• Duration: Continue daily until delivery 3, 4

Benefits of Low-Dose Aspirin

• 24% reduction in risk of preeclampsia in high-risk women 1, 5
• 14% reduction in risk of preterm birth 1, 5
• 20% reduction in risk of intrauterine growth restriction (IUGR) 1, 5
• Increases mean birthweight by approximately 130g 1, 5

Safety Profile

• Low-dose aspirin during pregnancy is considered safe and is associated with a low likelihood of serious maternal or fetal complications 3, 4
• No increased risk of placental abruption, postpartum hemorrhage, or fetal intracranial bleeding 1, 5
• No significant differences in cesarean delivery rates between aspirin and placebo groups 5

Important Considerations and Cautions

• Regular-dose aspirin (325 mg) should be avoided during pregnancy, especially during the last trimester, as it may cause problems in the unborn child or complications during delivery 6
• Aspirin should not be used for prevention of early pregnancy loss, fetal growth restriction, stillbirth, or preterm birth in the absence of high risk factors for preeclampsia 3, 4
• Implementation of risk-factor screening checklists in prenatal care can help ensure that all appropriate candidates receive aspirin prophylaxis 7

Clinical Algorithm for Aspirin Prophylaxis in Pregnancy

1. First prenatal visit: Screen all pregnant women for preeclampsia risk factors 3, 7
2. Risk assessment:
   • If any high-risk factor is present → Recommend low-dose aspirin 2, 3
   • If multiple moderate-risk factors are present → Recommend low-dose aspirin 3, 4
   • If no risk factors or only one moderate-risk factor → Aspirin not indicated 3, 4
3. Initiate aspirin: Start at 12-16 weeks of gestation 1, 5
4. Continue daily: Maintain therapy until delivery 3, 8
5. Monitor: No special monitoring required beyond routine prenatal care 5, 3