Those who are defined as infertile have failed to conceive after at least 12 months of regular unprotected intercourse. The chance of a normal couple conceiving is estimated at 20–25% per month, 75% by 6 months, and 90% at 1y.

Up to 50% of infertility is due to male factors. An estimated 14–25% of couples may be affected at some point in their reproductive years. Twenty-five percent of subfertile couples will have oligozoospermia and 10% azoospermia. Azoospermia exists in 1% of the male population.

Failed fertilization of the normal ovum due to defective sperm development, function, or inadequate numbers. There may be abnormalities of morphology (teratozoospermia, <4% normal forms), motility (asthenozoospermia, <40% motile sperm), low sperm numbers (oligozoospermia, <15 x 10 per mL), or absent sperm (azoospermia). Abnormal epididymal function may result in defective spermatozoa maturation or transport or induce cell death.

Causes: Functional sperm disorders: – immunological infertility (antisperm antibodies); head or tail defects; Kartagener’s syndrome (immotile cilia); dyskinetic cilia syndrome.