Cryptorchidism is when a boy’s testicle (or sometimes both testicles) doesn’t move down into the scrotum. The scrotum is the pouch of skin under the penis where the testicles are usually located. This condition is sometimes called “hidden” or “undescended” testicles. It’s not very common but is more likely to happen in boys who are born early (premature).

When a baby boy develops in the womb, the testicles form inside his abdomen near the kidneys. Around the seventh month of pregnancy, the testicles begin to move down toward the scrotum. For most boys, the testicles reach the scrotum by the time they are 6 months old.

The testicles have two main jobs:

Making sperm
Producing testosterone (the male sex hormone)

If a testicle doesn’t descend, it may still produce hormones, but it might not make sperm properly.

By the time a boy is 1 year old, about 1% of full-term baby boys still have an undescended testicle. Cryptorchidism is the most common birth condition affecting the male reproductive organs. Usually, only one testicle is affected, but in about 10% of cases, both testicles are undescended.

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