From the Guidelines
Low-dose aspirin (81 mg/d) should be used as preventive medication after 12 weeks of gestation in women who are at high risk for preeclampsia. This recommendation is based on the evidence from the US Preventive Services Task Force, which suggests that low-dose aspirin can help prevent morbidity and mortality from preeclampsia 1. The medication works by reducing inflammation and improving blood flow to the placenta, primarily by inhibiting the production of thromboxane and preserving prostacyclin.
Key Considerations
- Women at high risk for preeclampsia should start taking low-dose aspirin daily between 12 weeks of pregnancy and continue until delivery.
- High-risk factors include previous preeclampsia, chronic hypertension, diabetes, kidney disease, autoimmune disorders, or multiple gestation pregnancies.
- The medication should be taken at bedtime for optimal effect, as this timing aligns with the body's natural circadian rhythms of blood pressure regulation.
- Low-dose aspirin is generally considered safe during pregnancy at this dose, with minimal risks of bleeding complications.
Clinical Implications
- Women should only start this preventive therapy under medical supervision, as their healthcare provider needs to assess individual risk factors and determine if aspirin is appropriate for their specific situation.
- The USPSTF recommends the use of low-dose aspirin as preventive medication after 12 weeks of gestation in women who are at high risk for preeclampsia, with a B recommendation 1.
- The evidence suggests that low-dose aspirin can help prevent morbidity and mortality from preeclampsia, which is a serious health problem affecting pregnant women and contributing to both maternal and infant morbidity and mortality.
From the Research
Mechanism of Low-Dose Aspirin in Preventing Preeclampsia
- Low-dose aspirin can reduce the risk of preeclampsia and fetal growth restriction in high-risk pregnant women by balancing the levels of thromboxane A2 and prostacyclin, maintaining adequate uteroplacental blood flow, and improving placentation 2.
- Defective placentation resulting in a subsequent ischemic placenta is considered the starting point of preeclampsia, and low-dose aspirin initiated in early pregnancy can help prevent this condition 2.
Effective Dosage of Low-Dose Aspirin
- A daily dose of 150mg of aspirin is more effective than 75mg in preventing preeclampsia in high-risk pregnant women, with similar fetomaternal outcomes 3.
- A daily dose between 100 and 150 mg of aspirin taken in the evening should be initiated prior to 16 weeks of gestation and can be continued until delivery 4.
- The USPSTF 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.
Aspirin Non-Responsiveness
- Aspirin non-responsiveness, where individuals demonstrate insufficient antiplatelet effects, is not consistently identified in pregnant women at high-risk of pre-eclampsia when platelet function is assessed with COX-specific tests and aspirin adherence is accurately accounted for 6.
- Variable and indeterminate aspirin response indicates suboptimal adherence and/or dosing are more pressing factors to address to optimize aspirin effectiveness 6.
Benefits of Low-Dose Aspirin
- Low-dose aspirin use can reduce the risk for preeclampsia, preterm birth, small for gestational age/intrauterine growth restriction, and perinatal mortality in pregnant persons at high risk for preeclampsia 5.
- Low-dose aspirin can improve maternal vascular endothelial function without increasing the risks of adverse maternal and perinatal outcomes 2.