Normal conception requires that the man has a sufficient number of live sperm to enter the woman’s vagina, pass through the woman’s cervix and uterine cavity to reach the fallopian tubes; the woman is able to ovulate normally, her fallopian tubes are capable of picking up eggs and are open, and her uterus is normal and capable of conceiving a fetus. Problems in any of the above may cause infertility. Several epidemiological surveys have shown that male factors account for about 35% of infertility, female factors account for about 45%, unexplained infertility accounts for about 10%, and both men and women have problems accounting for 10%. In female infertility, tubal factors account for about 40%, ovulation factors account for about 40%, unknown causes account for about 10%, and the other 10% are uncommon factors, including uterine factors, cervical factors, immune factors, etc. 1, ovarian factors: ovarian insufficiency, luteal insufficiency, premature ovarian failure, polycystic ovary syndrome, ovarian tumors and other factors that affect follicle development or egg discharge can cause infertility. Ovulation disorders are the more common cause of female infertility. Without the development of mature follicles and ovulation, pregnancy is not possible. Ovulation disorders include complete absence of ovulation, rare ovulation or irregular ovulation, which can manifest clinically as amenorrhea, scanty menstruation or abnormal bleeding from the endometrium. Polycystic ovary syndrome is a result of ovulatory dysfunction caused by pituitary hormone abnormalities, leading to infertility. 2. Fallopian tube dysfunction: Under normal circumstances, the eggs discharged from the ovaries must be picked up by the umbrella of the fallopian tube. When the egg enters the fallopian tube, it is transported towards the uterine cavity by the movement of the cilia in the fallopian tube. In the 1/3 of the fallopian tube (abdominal region), the egg and sperm will merge and fertilize. After fertilization, the fertilized egg further divides to form an early embryo, which is transported to the uterine cavity and settles in the uterus on the 4th-5th day after ovulation (when it is close to the blastocyst stage). Therefore, the fallopian tubes have three functions: to pick up eggs, to provide nutrients for sperm-egg fertilization and early embryo development, and to transport eggs and embryos to the uterine cavity. When the fallopian tubes become inflamed due to bacterial infection, endometriosis or adhesions after surgery, the function of the tubes in picking up and transporting eggs can be affected. Bacterial infections can also damage the cilia in the fallopian tubes, preventing the embryo from being transported to the uterine cavity for proper implantation and providing the proper nutrients for early embryonic development. Infertility can occur when the fallopian tubes are dysfunctional and the sperm and egg cannot meet. 3. Cervical and uterine factors: congenital abnormalities, atresia or narrowing of the cervical canal, polyps, erosions, tumors and adhesions can affect the passage of sperm; the presence of anti-sperm antibodies in the cervical mucus, which are not conducive to sperm penetration of the cervical canal or completely render sperm inactive, can lead to the occurrence of infertility. 4. Immunological factors: It refers to the presence of anti-sperm antibodies in the female reproductive tract or serum, which cause sperm to agglutinate with each other and lose their vitality or die, leading to infertility or sterility. In addition, some infertile women have antibody-like substances against their own egg zona pellucida in their serum, which can prevent sperm from penetrating the egg for fertilization and can also cause infertility. 5. Central influence: imbalance of endocrine balance between the hypothalamus, pituitary and ovaries, pituitary tumor or scar can cause ovarian dysfunction and infertility; mental factors such as mental tension or excessive anxiety can affect the hypothalamic-pituitary-ovarian axis and inhibit ovulation causing infertility. 6, systemic diseases: such as severe malnutrition, or lack of certain important nutritional factors in the diet, can affect ovarian function and cause infertility; chronic diseases, metabolic diseases such as hypo- or hyperthyroidism, diabetes, adrenal dysfunction, etc. can also lead to infertility. 7, semen factors: prolonged liquefaction time of semen caused by urinary system diseases, sexually transmitted diseases and mumps, oligospermia, azoospermia, hematospermia, low sperm vitality, high malformation rate spermia, dead sperm, can reduce fertility and even cause infertility. 8, reproductive dysfunction: impotence, premature ejaculation, non-ejaculation, retrograde ejaculation, etc. caused by male organic factors impeding conduction, the influence of bad habits and negative mentality, can not lose sperm to the female cervical opening, resulting in male infertility. Sexual inhibition, sexual aversion, orgasmic disorder, painful intercourse and vaginal spasm in women can also affect the sperm-egg encounter, leading to infertility. 9, chromosomal factors: common are male pseudohermaphroditism, Creutzfeldt-Jakob syndrome and XYY syndrome. Chromosomal abnormalities need to be determined on a case-by-case basis. Some of them are infertile, even if conception is repeatedly miscarried after fetal stoppage, malformation, stillbirth, and cannot be successfully preserved, which is currently untreatable.