Ovulation disorders: congenital ovarian hypoplasia, PCOS, premature ovarian failure, functional ovarian tumors, ovarian chocolate cysts, gonorrhea, pituitary tumors, heavy malnutrition, hyperthyroidism, etc. Fallopian tube diseases: congenital hypoplasia, malformation of fallopian tubes, inflammation of fallopian tubes, post-operative fallopian tube surgery, etc. Uterine factor diseases: congenital malformation of the uterus, submucosal fibroids of the uterus can cause infertility or miscarriage after pregnancy; endometritis, endometrial tuberculosis, endometrial polyps, uterine adhesions or poor endometrial secretion response can affect fertilization of the egg. Cervical diseases: abnormal cervical mucus, cervical polyps, cervical fibroids, cervical orifice stenosis, severe cervical erosion. Vaginal factors: congenital absence of the vagina, transverse vaginal septum, hymenopexy, scarring of the vagina after injury, severe vaginal inflammation, etc. Immunologic factors: anti-sperm antibodies, anti-cardiolipin antibodies, anti-endometrial antibodies, anti-ovarian antibodies, anti-transparent band antibodies, anti-nuclear antibodies, lack of closed antibodies, ABO blood type incompatibility, RH blood type incompatibility, etc. Genetic factors: chromosomal abnormalities in the couple, chromosomal abnormalities in the embryo, etc.