In recent years, hot spots in preeclampsia research have focused on prediction and prevention. Evidence-based medical evidence suggests that low-dose aspirin has a preventive effect on preeclampsia. The United States, the United Kingdom, Canada, and the World Health Organization have written guidelines for the use of low-dose aspirin for the prevention of preeclampsia in high-risk pregnant women. The ability to effectively prevent the onset or progression of preeclampsia would undoubtedly be a major breakthrough in the perinatal field. Prior to 2013, evidence from randomized controlled trials (RCTs) and meta-analyses largely confirmed the role of low-dose aspirin in the prevention of preeclampsia in high-risk pregnant women, and that starting the drug before 16 weeks of gestation is preferable to starting it after 16 weeks of gestation. In Canada and the United Kingdom, low-dose aspirin was included in the guidelines for the prevention of preeclampsia in 2008 and 2010, respectively. In 2007, a meta-analysis published in the Cochrane database included 59 studies with 37,560 pregnant women and concluded that antiplatelet drugs reduced the risk of preeclampsia by 17%, especially in those with risk factors for preeclampsia. Based on this, the new 2013 American College of Obstetricians and Gynecologists guidelines for hypertensive disorders of pregnancy clearly suggest that aspirin 60-80 mg daily starting at the end of early pregnancy is recommended for pregnant women with early-onset preeclampsia and a history of preterm delivery before 34 weeks of gestation or a history of more than one episode of preeclampsia. In May 2014, a systematic evidence analysis published by the U.S. Preventive Services Task Force noted that the use of low-dose aspirin in mid-gestation A low-dose aspirin applied in midterm may prevent preeclampsia fetal growth restriction and preterm delivery. In September of the same year, the U.S. Preventive Services Task Force published guidelines on low-dose aspirin for the prevention of preeclampsia, recommending that pregnant women with risk factors for preeclampsia take prophylactic low-dose aspirin at 81 mg daily from 12 weeks’ gestation onward (recommendation level B). I. Risk factors for preeclampsia Risk factors for preeclampsia include a history of preeclampsia (especially in combination with adverse pregnancy outcomes), multiple pregnancies, chronic hypertension, type 1 or 2 diabetes, renal disease, and autoimmune disease. For those with high-risk factors, low-dose aspirin reduced the risk of preeclampsia by 24%, the risk of preterm delivery by 14%, and the risk of fetal growth restriction by 20%. For every 42 cases applied to people with high-risk factors, 1 case of preeclampsia was prevented. Intermediate risk factors for preeclampsia include primigravida, obesity (body mass index >30), family history of preeclampsia (mother, sisters), specific sociodemographic (African American, low-income population), age >35 years, personal medical history (e.g., low birth weight and small for gestational age infants, history of adverse pregnancies, gestational interval >10 years). Low-dose aspirin is also recommended for pregnant women with several intermediate risk factors, but the effect is not certain [7]. Prophylactic dosing is not recommended for low-risk pregnant women. Second, the method of application of aspirin 1. Dose: Based on the results of various RCTs, the dose of aspirin should be 60-150 mg/d. The most commonly used dose in the study was 100 mg, but the dose applied in the 2 RCTs with the largest sample size was 60 mg. Since aspirin tablets are available in the United States at 81 mg, this dose is recommended by the U.S. Preventive Services Task Force guidelines. There is no evidence of a dose-dependent effect of aspirin, and only 1 study showed that the effect of reducing preterm delivery was better at doses >75 mg than at doses <75 mg. The current dose of aspirin in China is 40 mg or 100 mg. Since there are no relevant RCT data in China, the appropriate dose for pregnant women in China is unclear, and it is recommended that 80 mg/d or 100 mg/d be given with reference to foreign studies. 2. Although previous studies suggested that dosing should be started before 16 weeks of gestation, a recent review by the U.S. Preventive Services Task Force summarized 15 studies and showed that there was no statistically significant difference in the preventive effect when dosing was started between 16 and 28 weeks of gestation (7 studies in total) compared with dosing started between 12 and 16 weeks of gestation (8 studies in total). No studies were retrieved to evaluate the effect of starting medication before 12 weeks of gestation. If preeclampsia has already occurred, the application of aspirin does not change the course of the disease. 3. Safety evaluation: Meta-analysis showed that the application of low-dose aspirin did not increase the risk of placental abruption, postpartum hemorrhage and intracranial fetal hemorrhage, nor did it increase the rate of perinatal morbidity and mortality. Although data on the long-term prognostic impact are lacking, it can be concluded that low-dose aspirin is safe and therefore does not require special monitoring. The timing of discontinuation varies among RCTs, with most stopping when labor is imminent, and some studies stopping before delivery, around 35 weeks of gestation, or when preeclampsia occurs. Although aspirin has no significant adverse effects, it is advisable to discontinue it 5-10 d before delivery to avoid an increased risk of intrapartum and postpartum hemorrhage (intraoperative hemorrhage increases by approximately 20% in those who do not discontinue it). If necessary, the platelet aggregation rate should be tested. III. Research directions Although aspirin has a positive effect on the prevention of preeclampsia, there are still many issues that need further research. For example, the most suitable population for aspirin, individual differences, identification of high-risk groups in primigravida, identification of high-risk pregnant women by serum predictors combined with medical history, benefits of treatment in intermediate-risk pregnant women, long-term effects of prophylactic use and benefits of continued use of the drug after delivery. In addition, the majority of the subjects in the various studies were Caucasians, with a minority of Blacks, and data on Asians are lacking. There is a lack of RCT evidence on the prevention of preeclampsia with aspirin in China. Although the "Guidelines for the diagnosis and treatment of hypertensive disorders in pregnancy (2012 edition)" in China did not mention about the prevention of preeclampsia, based on the new evidence of evidence-based medicine in this area in recent years, the use of low-dose aspirin after 12 weeks of gestation is important for the prevention of preeclampsia in high-risk pregnant women and the reduction of maternal and perinatal complications and mortality. The use of low-dose aspirin after 12 weeks of gestation has important implications for the prevention of preeclampsia in high-risk pregnancies and the reduction of maternal and perinatal complications and morbidity and mortality.