Causes of infertility include male factors, female factors, and “unexplained” factors. Common causes of infertility usually involve abnormalities within the female or male reproductive organs.
In males, 40%–50% of infertility cases have an unknown cause; 30%–40% are caused by primary hypogonadism (where the testes produce little-to-no testosterone); the remaining 10%–20% are caused by things such as impaired sperm transport due to obstruction, erectile dysfunction, and retrograde ejaculation. For female infertility, 40% of cases are caused by ovulation disorders attributed to aging, low ovarian reserve, endocrine disorders, polycystic ovary syndrome (PCOS), etc.; 30% are caused by obstruction of the fallopian tubes due to pelvic inflammatory disease, surgery, etc.; the remaining cases are caused by endometriosis and other conditions.[1]