What are the causes of infertility in human beings?

Explanation

Causes for male infertility:
(i) Undescended tests and swollen veins in scrotum
(ii) Underdeveloped testes
(iii) Tight clothing increases the temperature in scrotum and affect sperm production.
(iv) Autoimmune response against own sperm.
(v) Usage of alcohol, tobacco, marijuana drugs etc.
Causes for female infertility:
(i) Malformation of cervix or fallopian tubes.
(ii) Inadequate nutrition at puberty.
(iii) Low body fat (anorexia = psychological eating disorder due to fear of gaining weight).
(iv) Pelvic Inflammatory Disease (PID), uterine disorders, endometriosis.
(v) underdeveloped ovaries.
(vi) Developing antibodies against sperm.
Common Causes for both the sexes:
(i) Tumours in pituitary or sex organs
(ii) Inherited mutation of hormone synthesizing genes
(iii) Long term stress
(iv) Ingestion of toxins (Cadmium) & drugs
(v) Injuries to gonads
(vi) Ageing