Infertility refers to couples of childbearing age who have not used contraception after marriage, have a normal sexual life, and have not been able to conceive after 1 year of cohabitation. Infertility can be divided into primary infertility and secondary infertility according to whether the couple has suffered from infertility or not. Primary infertility refers to never having had a pregnancy; secondary infertility refers to having had a pregnancy and then not having another pregnancy without contraception for more than 1 year. Infertility is a reproductive disorder caused by many diseases or multiple factors, and it is not an independent disease, but a complex clinical syndrome. In recent years, the incidence of infertility has been increasing year by year. According to the data, the incidence of this disease is about 15%-20% of couples of childbearing age in developed countries in the world in recent years, and the incidence of infertility in China is conservatively estimated to be about 8%. This disease has become a global medical and sociological problem affecting human development and health. What are the causes of infertility? Before answering this question it is important to first understand the basic process of pregnancy. Conception is a complex physiological process that requires the following basic conditions: the woman’s ovaries emit normal eggs; the man produces normal sperm; the egg and sperm can meet in the fallopian tube and unite to form a fertilized egg and the fertilized egg can be transported smoothly to the uterine cavity; and the endometrium is suitable for the fertilized egg to settle. Among the various causes of infertility, female factors account for about 40-55%, male factors account for 25-40%, factors belonging to both sides account for 20%, and immune and unknown causes account for 10%. The specific causes are as follows: 1. male factors: male spermatozoa with few, weak or teratogenic sperm; 2. ovulation disorders: polycystic ovary syndrome; 3. pelvic factors: tubal obstruction, hydrocele, endometriosis, etc.; 4. uterine factors: endometrial tuberculosis, uterine diaphragm, etc.; 5. unknown causes.