Miscarriage is divided into spontaneous abortion and induced abortion. There are many causes of spontaneous abortion, mainly: 1. genetic defects 2. maternal factors (1) systemic diseases systemic infections, high fever, bacteria, viruses, severe anemia, chronic nephritis, hypertension. (2) Abnormalities of reproductive organs uterine malformation, uterine tumor, severe laceration of the cervix, relaxation of the inner cervical opening. (3) Endocrine abnormalities hypothyroidism, severe diabetes mellitus, luteal insufficiency. (4) Bad habits excessive smoking, alcoholism, excessive coffee drinking, heroin. (5) Traumatic stimulation severe shock, uterine trauma, excessive stress, anxiety, fear, sadness. (3) Abnormal immune function 4) Environmental factors Arsenic, lead, formaldehyde, benzene, chloroprene, ethylene oxide, etc.