Clinical considerations; 1. Indication population The recommended indication population is asymptomatic pregnant women at elevated risk for preeclampsia with no prior adverse reactions or contraindications to low-dose aspirin. 2. Pre-eclampsia risk assessment There is no method to identify women at high risk of pre-eclampsia based on biomarkers, clinical diagnostic tests, or medical history. Most clinicians identify women at risk based on medical history, and risk factors based on medical history may be helpful in guiding patients and physicians in their decision to initiate aspirin. Although the recommendation does not systematically review clinical risk assessment, the guideline gives some practical approaches (see table below). This approach may be helpful in identifying patients with an absolute risk of preeclampsia of at least 8%, which is also consistent with the lowest incidence of preeclampsia observed in the control group in the studies reviewed by the USPSTF. Women with 1 or more high-risk factors should receive low-dose aspirin therapy. Women with multiple intermediate risk factors may also benefit from low-dose aspirin, but the evidence for assessment using this method is inconclusive. Clinicians should assess the risk of preeclampsia and inform patients of the advantages and disadvantages of low-dose aspirin. Pre-eclampsia risk assessment risk class risk factors recommended high 1, previous history of pre-eclampsia, especially if accompanied by an adverse outcome 2, multiple pregnancies 3, chronic hypertension 4, type 1 or type 2 diabetes 5, renal disease autoimmune diseases (e.g., systemic lupus erythematosus or antiphospholipid antibody syndrome) Women with 1 or more risk factors should receive low-dose aspirin therapy in 1, not having children 2 , obese (BMI ≥30 kg/m2) 3, family history of preeclampsia (mother or sister) 4, sociodemographic characteristics (African American, lower socioeconomic) 5, age ≥35 years 6, personal past history (e.g., low birth weight or younger gestational age, previous pregnancies with adverse outcomes, pregnancies 10 years apart) Women with multiple moderate risk factors may be considered for low-dose Aspirin low previous full-term pregnancy smoothly not recommended low-dose aspirin. Assessment of adverse effects Low-dose aspirin for women at increased risk of preeclampsia does not increase the risk of placental abruption, postpartum hemorrhage, or fetal damage (intracranial hemorrhage or congenital anomalies). 4. The dose and timing of low-dose aspirin use varies across studies, but the benefits and harms of low-dose aspirin are consistent, and it is uncertain when to take or what dose of aspirin is of greater benefit. 5. Dosage Many randomized controlled trials have shown that 60-150 mg/d of aspirin reduces the risk of preeclampsia increases the risk of preeclampsia, preterm birth, and intrauterine growth retardation in women. The most commonly used dose is 100 mg/d, but the two largest trials estimated a benefit at 60 mg/d. Although 81 mg/d aspirin has not been evaluated in previous studies, the low-dose aspirin available in the United States is 81 mg in tablet form, which may be a reasonable dose for prophylaxis in women at risk for preeclampsia. Timing of low-dose aspirin is initiated at 12-28 weeks of gestation. For women at high risk of preeclampsia, the evidence does not show an additional benefit of early aspirin use (12-16 weeks) over delayed aspirin use (≥16 weeks). The American College of Obstetricians and Gynecologists recommends low-dose aspirin (60-80 mg/d) starting late in the first trimester for women with previous early onset preeclampsia and preterm delivery (<34 weeks) or more than 1 previous pregnancy with preeclampsia. The World Health Organization recommends low-dose aspirin (75 mg/d) starting at 12-20 weeks of gestation for women at high risk for preeclampsia, diabetes, chronic hypertension, renal or autoimmune disease, or multiple pregnancies. For other high-risk subgroups of women, there is limited evidence to recommend a benefit of low-dose aspirin. The UK National Institute for Health and Clinical Excellence (NICE) recommends aspirin (75 mg/d) from 12 weeks' gestation to delivery for women at high risk of preeclampsia, including previous pregnancies with hypertension, chronic kidney disease, autoimmune disease, type 1 or type 2 diabetes, or chronic hypertension. Recommendations for women with more than 1 intermediate risk factor, including age at first pregnancy ≥40 years, gestational interval >10 years, BMI ≥35 kg/m2, family history of preeclampsia, or multiple pregnancies, are the same as for high-risk patients. The American Heart Association and American Stroke Association recommend that women with chronic primary or secondary hypertension or previous pregnancy-related hypertension take low-dose aspirin from 12 weeks of gestation until delivery. The American Academy of Family Physicians recommends low-dose aspirin (81 mg/d) starting after 12 weeks of gestation for women at high risk for preeclampsia.