Testicles form inside your son's body in utero. They move from the body through a tube in the groin. Then they descend into the scrotum before birth. The scrotum is the sac of skin hanging behind the penis.
An undescended testicle stays in the abdomen. The testicle has not lowered into the scrotum before birth. This is called cryptorchidism.
The condition is common among baby boys who are born premature. All male babies are checked at birth to make sure their testicles have descended.
Often, the testicle will descend on its own within the first few months of life. If it does not, your child may need surgery.
Left untreated, an undescended testicle can cause fertility problems when the boy becomes an adult.
Other kinds of problems with testicles include:
A retractable testicle, which moves back and forth between the scrotum and the groin.
An ascending testicle, which moves back into the groin.
You can feel for your son's testicles while changing diapers or while bathing. If the testicle does not descend on its own by three or four months, your child may need surgery.