What is the role of Aspirin (acetylsalicylic acid) in twin pregnancy for preventing preeclampsia?

Role of Aspirin in Twin Pregnancy for Preventing Preeclampsia

Low-dose aspirin (81 mg/day) is recommended for all women with twin pregnancies starting at 12-16 weeks of gestation and continuing until delivery to prevent preeclampsia. 1

Risk Assessment and Rationale

Twin pregnancy is classified as a high-risk factor for preeclampsia according to multiple guidelines:

• The US Preventive Services Task Force (USPSTF) explicitly identifies multifetal gestation as a high-risk factor for preeclampsia 2
• The American College of Obstetricians and Gynecologists (ACOG) endorses this recommendation 2

Women with twin pregnancies have significantly higher rates of preeclampsia compared to singleton pregnancies due to:

• Increased placental mass
• Higher maternal cardiovascular demands
• Greater inflammatory response

Dosage and Administration

• Recommended dose: 81 mg daily (standard US dosage) 1
• When to start: Between 12-16 weeks of gestation, ideally before 16 weeks 1
• Duration: Continue until delivery 1

Starting aspirin before 16 weeks is critical as this is when placentation occurs. Beginning treatment after this period significantly reduces effectiveness 3.

Benefits of Aspirin Prophylaxis

Low-dose aspirin in high-risk women has been shown to:

• Reduce preeclampsia risk by 24% 2, 4
• Decrease preterm birth risk by 14% 2, 4
• Lower intrauterine growth restriction risk by 20% 2, 4

These benefits are particularly important for twin pregnancies, which already carry higher risks of these complications.

Mechanism of Action

Aspirin works by:

• Inhibiting cyclooxygenase-1 in the arachidonic acid pathway
• Decreasing thromboxane A2 production 2
• Balancing the ratio between thromboxane A2 (vasoconstrictor) and prostacyclin (vasodilator) 3, 5
• Improving uteroplacental blood flow and placentation 3

Safety Profile

Low-dose aspirin (≤100 mg daily) is considered safe during pregnancy:

• No increased risk of placental abruption or postpartum hemorrhage 4
• No increased risk of fetal intracranial bleeding 2
• No evidence of developmental harms in offspring by 18 months of age 2

Common Pitfalls to Avoid

1. Starting too late: Beginning aspirin after 16 weeks significantly reduces its effectiveness 1
2. Discontinuing too early: Aspirin should be continued until delivery 1
3. Inadequate dosing: While 81 mg is standard in the US, some European guidelines recommend 150 mg daily 1
4. Poor patient education: Emphasize the importance of daily adherence

Special Considerations

For twin pregnancies with additional risk factors such as:

• History of preeclampsia
• Chronic hypertension
• Type 1 or 2 diabetes
• Renal disease
• Autoimmune diseases

The recommendation for aspirin prophylaxis is even stronger, as these women have compounded risk 2, 1.

Conclusion

Twin pregnancy alone is sufficient indication for low-dose aspirin prophylaxis starting at 12-16 weeks gestation. The evidence clearly demonstrates benefits in reducing preeclampsia and its sequelae with minimal risks, making this a high-value intervention for improving maternal and fetal outcomes.