What is the relationship between Acetylsalicylic acid (Aspirin) and the risk of developing preeclampsia?

From the Guidelines

Low-dose aspirin is recommended for pregnant women at high risk for preeclampsia, starting between 12-16 weeks of gestation and continuing until delivery, with a typical dosage of 100-150 mg daily. This recommendation is based on the most recent and highest quality study available, which suggests that low-dose aspirin can reduce the risk of preeclampsia by approximately 10-30% in high-risk women with minimal side effects 1. Women considered high risk include those with previous preeclampsia, multifetal pregnancy, chronic hypertension, type 1 or 2 diabetes, renal disease, or autoimmune disorders like lupus. Moderate risk factors include first pregnancy, maternal age over 35, BMI over 30, family history of preeclampsia, and sociodemographic characteristics.

Key Considerations

• Aspirin works by inhibiting thromboxane production while preserving prostacyclin, improving the balance between these compounds that affects placental development and blood flow 1.
• The medication should be started early because placentation occurs in the first trimester, and aspirin's preventive effects are most beneficial when begun before placental development is complete.
• The evening dosing schedule aligns with circadian rhythms of blood pressure regulation for maximum effectiveness.
• A dosage of 162 mg/day may be acceptable, but currently, in the U.S., low-dose aspirin is available in 81-mg tablets, which may not be sufficient to reduce preeclampsia risk 1.

High-Risk Groups

• Pregnant individuals with type 1 or type 2 diabetes should be prescribed low-dose aspirin 100–150 mg/day starting at 12 to 16 weeks of gestation to lower the risk of preeclampsia 1.
• Individuals with gestational diabetes mellitus (GDM) may be candidates for aspirin therapy for preeclampsia prevention if they have a single high risk factor or multiple moderate risk factors.

Research Gaps

• Further research is needed to determine the effect of low-dose aspirin on the development of preeclampsia and how the magnitude of response to low-dose aspirin varies with individual or combined risk factors for preeclampsia 1.

From the FDA Drug Label

If pregnant or breast-feeding ask a health professional before use. it is especially important to use aspirin during the last 3 months of pregnancy unless definitely directed to do so by a doctor because it my cause problems in the unborn child or complications during delivery. The FDA drug label does not answer the question.

From the Research

Aspirin Dosage and Preeclampsia Risk

• The American College of Obstetricians and Gynecologists recommends 81 mg of aspirin daily for women at risk of preeclampsia between 12 and 28 weeks' gestation 2.
• The World Health Organization recommends 75 mg of aspirin daily for women at high risk of preeclampsia, initiated before 20 weeks of gestation 2.
• A randomized controlled trial found that 150 mg of aspirin daily was more effective than 75 mg daily in preventing preeclampsia in high-risk pregnant women 3.
• A network meta-analysis of 23 randomized controlled trials suggested that a dosage of 80-100 mg/day may be the optimal dosage for preventing preeclampsia in high-risk pregnant women 4.

Timing of Aspirin Initiation

• The Royal College of Obstetricians and Gynaecologists and the National Institute of Health and Care Excellence recommend initiating low-dose aspirin at 12 weeks of gestation for women at increased risk of preeclampsia 2.
• The International Federation of Gynecology and Obstetrics initiative on preeclampsia recommends initiating 150 mg of aspirin at 11 to 14+6 weeks' gestation 2.
• A study found that doses of >100 mg of aspirin daily initiated before 16 weeks' gestation seem to be most effective at reducing the risk of preeclampsia 2.

Safety and Efficacy

• The US Preventive Services Task Force recommends the use of low-dose aspirin (81 mg/d) as preventive medication for preeclampsia after 12 weeks of gestation in persons who are at high risk for preeclampsia 5.
• A case report described the occurrence of cerebral hemorrhage and intraventricular hemorrhage in a pregnant woman taking 100 mg aspirin daily, highlighting the potential risks of aspirin use in pregnancy 6.
• A network meta-analysis found that aspirin significantly reduced the incidence of preeclampsia, with no significant differences in the occurrence of postpartum hemorrhage, small for gestational age, placental abruption, and intrauterine growth restriction between women taking aspirin and those taking placebos 4.