Inclusion Criteria:  1. Women with preeclampsia:  Singleton women who meet the diagnostic criteria for preeclampsia. No previous history of major disease. Body mass index is between 23-25kg/m2. 20-45 years old. 22-42 weeks of gestation. Participate in the test voluntarily and sign the informed consent.  2. Healthy pregnant women:  In good health, no history of major diseases before pregnancy, pregnant women and single mothers with healthy fetuses (newborn) after pregnancy and delivery. Body mass index is between 23-25kg/m2. 20-45 years old. 22-42 weeks of gestation.  Participate in the test voluntarily and sign the informed consent.  Exclusion Criteria:  1. Women with preeclampsia:  Patients with essential hypertension. Pregnant women with high blood glucose before and/or during pregnancy. Convulsions on the basis of preeclampsia that cannot be explained by other reasons. Women with primary disease due to other non-preeclampsia diseases before and after pregnancy, such as cardiovascular, cerebrovascular, liver, kidney, hematopoietic, endocrine, immune, precancerous lesions or cancers, including the reproductive system. Twin or multiple births. Pregnant women with mental disorders or mental diseases. Using illegal drugs before and after pregnancy. Persons with sexually transmitted diseases or infectious diseases. Pregnant women receiving prenatal steroid therapy.  2. Healthy pregnant women:  Patients with severe maternal and/or fetal (newborn) adverse events during or after the third trimester of pregnancy or delivery. Such as intrauterine infection, amniotic fluid embolism and other serious maternal adverse events; Fetal malformation, fetal growth restriction, fetal intrauterine distress, neonatal hemolysis and other serious fetal (neonatal) adverse events. Pregnant women with other diseases before and after pregnancy, such as cardiovascular and cerebrovascular, liver, kidney, hematopoietic system, endocrine system, immune system, precancerous lesions or cancer, including the reproductive system, and other serious primary diseases. Women with a clear cause of premature delivery. Twin or multiple births. Pregnant women with mental disorders or mental diseases. Use illegal drugs before and after pregnancy. Persons suffering from sexually transmitted diseases or infectious diseases. Pregnant women receiving prenatal steroid therapy.