The focus of the four coagulation tests is mainly on prothrombin time, prothrombin activity, fibrinogen, and D-dimer. In general, the clinical reference for prothrombin activity is relatively small, and the more meaningful reference item is the concentration of fibrinogen. The concentration of fibrinogen in pregnant women is generally higher than that of normal people, with fibrinogen concentrations in normal people ranging from 2-4 g/L and in pregnant women often >4 g/L. D-dimer is also a meaningful test during pregnancy, but there is no standard value for D-dimer during pregnancy. The concentration of D-dimer in the normal population is usually <500 μg/L, but it varies among pregnant women. In some pregnant women, the concentration of D-dimer can be more than 1000 μg/L. If the concentration of D-dimer in pregnant women is more than 2000 μg/L, it is obviously abnormal. Therefore, the obstetrics department also tracks the D-dimer dynamically in pregnant women according to their individual differences. The prothrombin time is mainly used for the follow-up of anticoagulation therapy during pregnancy. For prothrombin activity, the clinical reference is mainly by the doubling of prothrombin time to see if coagulation is impaired. If coagulation disorders are present, the pregnant woman must actively search for the cause and treat the cause or terminate the pregnancy in a timely manner. Diseases that cause coagulation disorders, such as acute fatty liver during pregnancy, as well as severe hepatitis and cirrhosis, are often more dangerous for pregnant women. HELLP syndrome may also cause coagulation disorders, so coagulation tests are more important during pregnancy.