Lead: Infertility is caused by the following reasons: vagina, cervix, uterus, fallopian tube, ovary, endocrine and congenital factors. 1. Vaginal factors Obstacles or difficulties in sexual intercourse caused by congenital factors such as vaginal atresia or vaginal septum, thus affecting the entry of sperm into the female reproductive tract. Furthermore, vaginal inflammation caused by mold, trichomonas, gonococcus and other infections changes the vaginal biochemical environment and reduces the motility and vitality of sperm, thus affecting the chances of pregnancy. 2, cervical factors, cervical stenosis, polyps, tumors, adhesion and so on. Can affect sperm passage; Cervical erosion, its inflammatory exudate has spermicidal effect; The existence of anti-sperm antibody in cervical mucus is not conducive to sperm penetration into cervical canal or complete loss of sperm mobility. It is worth noting that cervical adhesion caused by induced abortion of unmarried pregnant women is more likely to cause this serious complication, especially in repeated abortion, which keeps sperm out of the cervix. Congenital abnormality of cervical canal is often accompanied by abnormal menstruation or dysmenorrhea, and girls will go to the hospital for examination after menarche. Cervicitis caused by Neisseria gonorrhoeae often leads to atresia or stenosis of cervical canal through sexual infection. Relaxation of cervical internal orifice is one of the common causes of infertility caused by habitual late abortion. When the gestational age increases and the weight of the fetal sac increases beyond the capacity of the cervical canal, the cervical canal expands, the fetal sac bulges and breaks water, and the fetus and placenta are discharged one after another, which often occurs after 3 months of pregnancy. 3. Uterine factors Congenital hypoplasia, immature uterus and solid uterus without uterine cavity will all affect women's fertility. Uterine retroflexion or severe retroflexion, endometrial inflammation and intrauterine adhesions are all causes of infertility. About 75% patients with endometriosis have a history of infertility, which is because it can cause posterior adhesion of uterus, poor mobility and tubal adhesion, leading to decreased peristalsis; Ectopic endometrium can be used as an autoantigen, which can cause female immune hyperfunction, such as producing anti-endometrial antibodies; Ectopic endometrium can also produce more prostaglandins, leading to strong contraction of uterus and fallopian tube muscles, interfering with the operation of sperm and eggs and the implantation of pregnant eggs, thus causing infertility. Uterine leiomyoma is the most common benign tumor in women, and the infertility rate of patients with uterine leiomyoma can reach 30-40%, which is much higher than that of the general population. Among them, submucosal myoma can affect sperm passage and blastocyst implantation, while intramural myoma not only affects pregnancy, but also often causes abortion or premature delivery. Even if pregnant, in the third trimester, abnormal uterine contractility will cause premature delivery, hinder delivery or cause postpartum hemorrhage. 4. Tubal factors The fallopian tube is too long or narrow, and tubal inflammation causes lumen occlusion, water accumulation or adhesion, which will hinder the operation of sperm, eggs or fertilized eggs. Tubal diseases can account for 25% of female infertility, which is an important cause of infertility. Inflammatory diseases include tuberculosis, endometriosis, trichomoniasis, gonorrhea and other pathogenic infections. Obstructed fallopian tubes can be recanalized by hysteroscopy, drainage and microsurgical plastic surgery, and patients can also get pregnant by in vitro fertilization-embryo transfer technology. 5, ovarian factors ovarian follicle hypoplasia, failure to ovulate to form corpus luteum, premature ovarian failure, polycystic ovary, ovarian tumor and other factors that affect follicular development or egg excretion will cause infertility. For example, follicles can mature but can't rupture, so eggs can't be discharged, their basal body temperature is normal, and the changes of hormone levels in the blood are completely normal. This disease is called unruptured follicle syndrome. Luteal insufficiency is the expression of insufficient progesterone secretion, and most of the reasons are related to the high level of prolactin. At this time, the development of endometrial secretion period is affected, which is not conducive to the implantation of fertilized eggs. Even if it can be implanted, it will be aborted because of insufficient progesterone secretion. Polycystic ovary syndrome is anovulatory, not a single disease, but a series of clinical symptoms and signs, mostly manifested as menstrual disorder (rare menstruation or amenorrhea); Infertility; Bilateral ovarian enlargement, capsule thickening and polycystic change; Hairiness, obesity, increased sexual desire. Infertility caused by endocrine and menstrual disorders. 6. Endocrine factors When the hypothalamus is immature or the central maturation of the hypothalamus cycle is delayed, the adjustment between the hypothalamus-pituitary-ovary axis is not perfect, so it shows anovulatory menstruation, amenorrhea or luteal insufficiency, which are all possible reasons for infertility. In addition, hyperthyroidism or hypothyroidism, hyperthyroidism or hypothyroidism will also affect ovarian function and hinder ovulation. 7. Congenital hypoplasia of reproductive system is accompanied by serious congenital factors, and such patients are often accompanied by primary amenorrhea. Sex chromosome abnormalities, such as Turner syndrome, true and false hermaphroditism. Habitual abortion caused by chromosome abnormality, etc. 8, systemic factors, nutritional disorders, metabolic diseases, chronic wasting diseases, simple obesity, etc. Physical factors such as taking raw cottonseed oil, toxic chemical reagents, radiation exposure, microwave, etc. 9. Psychoneurological factors: autonomic nervous system dysfunction, psychosis, environmental amenorrhea, anorexia nervosa, pseudopregnancy, etc. 10, other immune infertility, blood group incompatibility (such as habitual abortion or stillbirth caused by Rh factor or ABO hemolysis). Immune infertility accounts for about 10-30% of infertile patients, including anti-sperm antibody, anti-endometrial antibody, anti-egg antibody and other immune infertility. But the most common one in clinic is immune infertility caused by the production of anti-sperm antibodies. Due to female genital tract inflammation, local exudation increases and immune-related cells enter the reproductive tract. At the same time, the permeability of reproductive tract mucosa changed, which enhanced the absorption of sperm antigen. In addition, infectious agents such as bacteria and viruses can be used as natural adjuvants to enhance the immune response of the body to sperm antigens. Then, anti-sperm antibodies appear in local genital tract and blood debt, which affects sperm motility, interferes with fertilization and leads to infertility.