When a testicle remains in the abdomen. Testicles are not formed in the scrotum, but in the abdomen. Before birth, they usually descend into the scrotum. About 3.5% of the time, a testicle doesn’t descend into the scrotum, so the boy is born with an undescended testicle. The majority of undescended testicles self-correct on their own during the first year. Men with a history of having an undescended testicle have a greater risk for infertility and cancer of the testicles.