What are the pros and cons of using aspirin (acetylsalicylic acid) in pregnancy for preventing preeclampsia?

From the Guidelines

Low-dose aspirin (60-150 mg daily) is recommended for pregnant women at high risk for preeclampsia, as it reduces the risk of preeclampsia by 24%, preterm birth by 14%, and intrauterine growth restriction (IUGR) by 20%. The benefits of aspirin in preventing preeclampsia are well-established, with a substantial reduction in risk for women at increased risk for preeclampsia 1. The advantages of aspirin include its widespread availability, low cost, and well-established safety profile.

Some of the key benefits of aspirin in pregnancy include:

• Reduction in risk of preeclampsia by 24%
• Reduction in risk of preterm birth by 14%
• Reduction in risk of IUGR by 20%
• Improvement in placental blood flow and reduction in inflammation

However, aspirin also has potential drawbacks, including:

• Gastrointestinal irritation
• Increased bleeding risk
• Allergic reactions in sensitive individuals
• Not universally effective and provides only partial risk reduction

It's essential to note that aspirin should be avoided in women with bleeding disorders, active peptic ulcer disease, aspirin allergy, or liver disease. The decision to use aspirin should be made in consultation with a healthcare provider who can properly assess individual risk factors and potential benefits 1.

In terms of the optimal dosage and timing of aspirin, the evidence suggests that low-dose aspirin (60-150 mg daily) should be started between 12-16 weeks of gestation and continued until delivery 1. Overall, the benefits of aspirin in preventing preeclampsia outweigh the risks, and it is a recommended treatment for pregnant women at high risk for preeclampsia.

From the Research

Pros of Aspirin in Pregnancy for Prevention of Preeclampsia

• Aspirin at doses below 300 mg selectively and irreversibly inactivates the cyclooxygenase-1 enzyme, suppressing the production of prostaglandins and thromboxane and inhibiting inflammation and platelet aggregation, which can help prevent preeclampsia 2
• An individual patient data meta-analysis has indicated a modest 10% reduction in preeclampsia rates with the use of aspirin 2
• The Aspirin for Evidence-Based Preeclampsia Prevention trial has revealed that aspirin at a daily dosage of 150 mg, initiated before 16 weeks of gestational age, and given at night to a high-risk population, identified by a combined first trimester screening test, reduces the incidence of preterm preeclampsia by 62% 2
• A secondary analysis of the Aspirin for Evidence-Based Preeclampsia Prevention trial data also indicated a reduction in the length of stay in the neonatal intensive care unit by 68% compared with placebo, mainly because of a reduction in births before 32 weeks of gestational age with preeclampsia 2
• Daily low-dose aspirin during pregnancy was associated with lower risks of serious perinatal outcomes for individuals at increased risk for preeclampsia, without evident harms 3
• Low-dose aspirin can prevent preeclampsia and early-preeclampsia, and its efficacy is dose-dependent 4

Cons of Aspirin in Pregnancy for Prevention of Preeclampsia

• The use of aspirin in the third trimester has been reported to cause hemostatic abnormalities in both mother and neonate 5
• Other complications associated with prostaglandin synthetase inhibitors include premature closure of the ductus and neonatal primary pulmonary hypertension 5
• The effect size of aspirin has been found to be more pronounced in women with good compliance to treatment, which may be a challenge for some patients 2
• Randomized trials are underpowered to investigate the treatment effect of aspirin on the rates of other placental-associated adverse outcomes such as fetal growth restriction and stillbirth 2
• There is a need for large, well-designed, and adequately powered randomized-controlled trials to confirm the efficacy and safety of aspirin for preventing preeclampsia 6

Key Considerations

• Aspirin dosages ranged from 50 mg/d to 150 mg/d in most trials, and the optimal dosage for preventing preeclampsia is still unclear 2, 3, 4
• The incidence of preeclampsia among the trials of participants at increased risk ranged from 4% to 30%, highlighting the importance of identifying high-risk patients 3
• The beneficial effect of aspirin has been found to be similar in subgroups according to different maternal characteristics, except for the presence of chronic hypertension, where no beneficial effect is evident 2