The failure of the testicles (or “testes”) to descend into the scrotum (the skin sac below the penis) is called “cryptorchidism”. It is also called having hidden or undescended testicles. The condition is generally uncommon but often affects boys born prematurely.
As a male foetus grows, the testicles appear in the abdomen near the kidneys. During the seventh month of development, the testicles start to descend to the groin. They should reach their final position in the scrotum by 6 months after birth.
The testicles make sperm and testosterone, the male sex hormone. An undescended testicle may produce hormones, but the ability to make sperm is disrupted.
At 1 year of age, nearly 1% of all full-term male infants have cryptorchidism. This is the most common birth defect of the sex organs in newborn male infants. Usually, only one testicle is affected, but both testicles are undescended in about 10% of children with cryptorchidism.