Sometimes a child is born with the testes in the scrotum, but they develop undescended testes later. As the child grows, the spermatic cord fails to grow at the same rate. It ends up too short, and pulls the testis back up into the groin. This can happen between one and 10 years of age.

The final descent of the testis may take up to six months after birth, but usually occurs within three months of birth. If a testicle has not reached the scrotum by the time the baby is 6 months of age, it is considered an undescended testicle. This can occur to one or both testicles.

This condition is fairly common, occurring in 3 percent to 5 percent of full-term boys at birth, with a much higher incidence in premature infants. However, the majority of undescended testicles will descend to a normal position within the first three to six months of life.

Undescended testicles are diagnosed at three months of age if the testicle has failed to descend into the scrotum by that time. Undescended testicles are diagnosed by physical examination. In some cases, the missing testicle can be felt in the lower abdomen.

The testes may come down after birth, during the baby's first three to six months. If the testes have not descended by then, they are likely not to not come down. If your child has an undescended testis when he is over 6 months of age, he will need an operation to place it in the correct position.