The etiology of miscarriage includes embryonic factors, maternal factors, paternal factors and environmental factors. 1, embryonic factors: embryonic or fetal chromosomal abnormalities are the most common cause of early miscarriage, accounting for about 50%-60%, mid-term pregnancy miscarriage accounts for about 1/3, and late pregnancy fetal loss accounts for only 5%. 2, maternal factors: (1) systemic diseases: pregnant women suffering from systemic diseases, such as serious infections, hyperthermic diseases, severe anemia or heart failure, thrombotic diseases, chronic wasting diseases, chronic liver and kidney diseases or hypertension, etc., may lead to miscarriage. (2) Genital abnormalities: uterine malformation, uterine fibroids, uterine adenomyosis, uterine adhesions, etc., can affect the embryo’s implantation and development and lead to miscarriage. Cervical insufficiency caused by severe cervical laceration, partial or total cervical excision, and relaxation of the inner cervical opening can lead to premature rupture of the fetal membranes and late miscarriage. (3) Endocrine abnormalities: female endocrine function abnormalities (such as luteal insufficiency, hyperprolactinemia, polycystic ovary syndrome, etc.), hypothyroidism, and poor glycemic control in diabetes can lead to miscarriage. (4) Strong stress and bad habits: bad stimulation during pregnancy, no matter serious physical (such as surgery, direct abdominal impact, too frequent sexual intercourse) or psychological (excessive tension, anxiety, fear, sadness and other mental trauma) can lead to miscarriage. Pregnant women who smoke excessively, drink alcohol, drink too much coffee and take drugs may lead to miscarriage. (5) Abnormal immune function: including abnormal autoimmune function and abnormal alloimmune function. Clinically, it may only manifest as spontaneous miscarriage or even recurrent miscarriage, or there may be rheumatic immune diseases (such as systemic lupus erythematosus, etc.) at the same time; a few occur in pregnant women with positive antinuclear antibodies and positive antithyroid antibodies. 3. Paternal factors: Some studies have confirmed that chromosomal abnormalities of sperm can lead to spontaneous abortion. However, there is no clear evidence whether abnormally high sperm malformation rate is related to spontaneous abortion in clinical practice. 4, environmental factors: excessive exposure to radiation and chemicals such as arsenic, lead, formaldehyde and benzene may cause miscarriage.