Low-Dose Aspirin for Preeclampsia Prevention in IVF Pregnancies
Low-dose aspirin is not recommended for all IVF pregnancies, but should be prescribed for those with additional risk factors for preeclampsia according to ACOG and USPSTF guidelines. 1, 2, 3
Risk Assessment for Aspirin Therapy in IVF Pregnancies
IVF alone is not specifically listed as a high-risk factor for preeclampsia in current guidelines, but assisted reproduction is mentioned as a consideration. The decision to prescribe low-dose aspirin should be based on the presence of:
High-Risk Factors (any one warrants aspirin therapy):
- History of preeclampsia
- Multifetal gestation
- Chronic hypertension
- Type 1 or type 2 diabetes
- Renal disease
- Autoimmune diseases (such as systemic lupus erythematosus)
- Antiphospholipid syndrome
Moderate-Risk Factors (more than one warrants aspirin therapy):
- First pregnancy
- Maternal age ≥35 years
- BMI >30 kg/m²
- Family history of preeclampsia
- Sociodemographic risk factors
Dosing and Timing Recommendations
When indicated, the recommended regimen is:
- Dose: 81 mg daily (ACOG/USPSTF recommendation) 1, 2
- Initiation: Between 12-16 weeks gestation (optimally before 16 weeks)
- Duration: Continue until delivery
It's worth noting that European guidelines recommend a higher dose of 150 mg daily, and some evidence suggests that doses >100 mg may be more effective 1, 4. Recent research indicates that both dosage and timing of initiation are critical factors in aspirin's effectiveness for preeclampsia prevention 4.
Mechanism and Efficacy
Low-dose aspirin works by inhibiting thromboxane A2 (a vasoconstrictor) while promoting prostacyclin (a vasodilator), which improves placental perfusion during critical placentation 1. When initiated before 16 weeks, aspirin can reduce:
- Overall preeclampsia by 43%
- Severe preeclampsia by 53%
- Fetal growth restriction by 44%
- Preterm birth risk by 14% 1
Special Considerations for IVF Pregnancies
Studies in women undergoing IVF have shown that preconception low-dose aspirin is associated with improved implantation rates and increased blood flow velocity in uterine and ovarian arteries 5. Some evidence suggests that preconception initiation of aspirin (75-100 mg) is safe in pregnancy 5.
Common Pitfalls to Avoid
- Timing errors: Starting aspirin too late (after 16 weeks) reduces its effectiveness 1
- Inadequate risk assessment: Failing to identify all relevant risk factors may lead to missed opportunities for prevention 6
- Insufficient dosing: The standard 81 mg dose may be inadequate for some high-risk patients 4
- Early discontinuation: Aspirin should be continued until delivery 1, 2
- Overlooking patients with multiple moderate risk factors: These patients are least likely (0-6%) to receive indicated aspirin prophylaxis despite meeting criteria 6
Low-dose aspirin is generally considered safe during pregnancy with minimal risks of serious maternal or fetal complications 2, 3. When preeclampsia prevention is indicated, the benefits of aspirin therapy outweigh the potential risks.