Conception is a complex physiological process that requires the following conditions: the ovaries discharge normal eggs; the semen is normal and contains a significant number of normal sperm; the egg and sperm are able to meet in the fallopian tube and unite to become a fertilized egg, which is successfully transported into the uterine cavity; and the endometrium is sufficiently prepared for the fertilized egg to implant. Abnormalities in any of these components can prevent conception.
A normal couple of childbearing age with a normal conjugal life without any contraceptive measures who do not conceive within 1 year is said to be infertile. The study concluded that among the causes of infertility, female factors account for 43.16, male factors account for 26.40, male and female factors account for 24.51 and unknown factors account for 5.93%, of course, modern society is too stressful, lifestyle changes and increasingly serious environmental pollution and other factors have also played a role in infertility.
1.Female factors
Fallopian tube factor
The fallopian tubes have the role of transporting sperm, taking in eggs and sending fertilized eggs into the uterine cavity. Tubal factors are the main cause of female infertility, accounting for about 20.0-32.8. There are many causes of tubal infertility, including pelvic infectious diseases, endometriosis and congenital tubal abnormalities. Among them, pelvic adhesions caused by pelvic infectious diseases are the main factors leading to tubal infertility. In recent years, the incidence of tubal infertility has been increasing year by year due to the increase in the incidence of sexually transmitted diseases and the rate of abortion.
Ovarian factors
Ovarian factors include ovulatory factors and endocrine factors. Anovulation is one of the most serious causes of infertility. Factors that cause ovarian dysfunction leading to persistent anovulation include
(i) ovarian pathology, such as congenital ovarian hypoplasia, polycystic ovary syndrome, etc.
(ii) Hypothalamic-pituitary-ovarian axis dysfunction, including hypothalamic anovulation and anovulation due to pituitary dysfunction.
③ systemic factors, such as malnutrition, obesity, hyperthyroidism, etc. affecting ovarian function leading to anovulation.
Uterine factors
Congenital malformation of the uterus and submucosal fibroids can lead to infertility or miscarriage after pregnancy; poor endometrial secretion response and endometritis can affect the passage of sperm, which can also cause infertility.
Cervical factors
The cervical canal is a channel for the upward movement of sperm, and its anatomical structure and the secretory properties of cervical mucus have a close relationship with fertility. Cervical stenosis or congenital abnormal cervical development can affect the entry of sperm into the uterine cavity. Cervical inflammation can alter the amount and properties of cervical mucus, affecting sperm vitality and the number of sperm entering the uterine cavity. In chronic cervicitis, cervical mucus thickens and contains a large number of white blood cells, which is not conducive to sperm viability and penetration and can affect conception.
Vaginal factors
Congenital absence of the vagina and damage to the vagina can interfere with intercourse and prevent sperm entry. In severe vaginitis, the pH of the vagina is altered, reducing the viability of sperm and shortening their survival time, which can affect conception. In some women, infertility is caused by immune factors that destroy sperm cells in the vagina, preventing sperm from entering the egg and preventing conception.
Age Factors
Fertility in women starts to decline from the age of 35, and declines more rapidly after 37. As age increases, the incidence of infertility increases and fertility decreases, as evidenced by lower pregnancy rates, increased miscarriage rates, longer average intervals between births, increased probability of chromosomal abnormalities in the conceived offspring, and lower live birth rates.
2.Male partner factors
Semen abnormalities
It mainly refers to oligospermia, weakness and teratogenesis. Many factors can affect the number, structure and function of spermatozoa:
①Acute or chronic diseases: such as mumps with orchitis leading to testicular atrophy
②External genital infections: e.g. gonorrhea infection
③Congenital abnormal development: such as congenital testicular hypoplasia
④Excessive exposure to chemical substances: such as pesticides, lead, arsenic, etc.
⑤ Therapeutic factors: e.g. chemotherapy and radiation therapy leading to infertility
(6) Excessive alcohol abuse
⑦ Drug abuse: including marijuana and cocaine
⑧ Excessive local scrotal temperature: such as prolonged sauna bathing
Obstruction of the vas deferens and obstruction of sperm transport
The main causes are infection of the reproductive ducts and trauma to the reproductive ducts, such as orchitis and epididymitis, vas deferens and prostate infection, etc. Pelvic, inguinal and perineal surgery can cause narrowing of the vas deferens and obstruction of sperm transport.
Immunological factors
Antibodies against sperm in the male body can cause male infertility, and the ejaculated sperm can not pass through the female cervical mucus due to self-agglutination.
Endocrine factors
Male endocrine secretion is regulated by the hypothalamic-pituitary-testicular axis, and the dysfunction of this axis may affect sperm production and cause infertility.
Erectile abnormalities
Erectile abnormalities prevent sperm from entering the female vagina. Male erection is affected by both physical and psychological factors. Common physiological factors include congenital external genital malformation, genital inflammation, endocrine diseases, chronic renal failure, etc.; psychological factors include mental and emotional abnormalities and incompatible family relationships.
3, both male and female factors
Lack of basic knowledge of sexual life
Both men and women lack the basic knowledge of sexual life, the couple does not understand the anatomy and physiological structure of the reproductive system and lead to incorrect sexual life.
Immunity factors
There are two types of immune conditions that affect conception.
(1) Homoimmunity: sperm, seminal plasma or fertilized eggs are antigenic substances that are absorbed by the vagina or endometrium and produce antibody substances through immune reactions, so that sperm and eggs cannot combine or fertilized eggs cannot be laid.
Autoimmunity: The presence of autoantibodies to the zona pellucida in the serum of infertile women can prevent sperm from penetrating the egg after reacting with the zona pellucida, thus affecting fertilization.
4. Other factors
Mental factors
Work pressure, economic burden, family illness, depression, fatigue, etc. can lead to psychological disorders and infertility. In addition, the couple’s excessive expectation of pregnancy and sexual tension can also cause psychological stress leading to infertility.
Environmental factors
Every year, humans release a large number of toxic chemicals into the environment, which can interfere with the synthesis, secretion, transfer, binding and digestion of natural hormones in the body, thus altering endocrine secretion, such as synthetic medicinal estrogens, pesticides, industrial chemicals and heavy metals.
A study in Japan found that female quail exposed to DDT can lead to disruption of their reproductive system, thereby reducing their hatching rate; a study in Taiwan, China, showed that women exposed to low doses of radioactive cobalt will lead to a reduction in their fertility; a study in India showed that, compared with women with low levels of arsenic in drinking water, high concentrations of arsenic in drinking water will increase the risk of spontaneous abortion and the occurrence of stillbirths .
Understanding the causes of infertility can provide a reliable basis for taking measures to prevent infertility in advance and for the treatment of infertility patients.