In recent years, the incidence of thromboembolism in pregnancy is increasing, which is one of the main causes of maternal mortality. In 2018, the American College of Obstetricians and Gynecologists updated its guidelines to provide information regarding the high-risk factors, use of anticoagulant drugs in pregnancy, diagnosis, intrapartum / postnatal management, and so on, and this Practice Bulletin replaces Practice Bulletin No. 123 (2011). The clinical recommendations from the ACOG guidelines are interpreted according to evidence-based practices, in order to better guide the clinical work.