Cryptorchidism: an apparent substantial increase since 1960. John Radcliffe Hospital Cryptorchidism Study Group.

A total of 1849 boys born to mothers resident in a defined area around Oxford were examined for cryptorchidism. Those born in hospital were examined at birth and again after three months if cryptorchid at the earlier examination. The incidence of cryptorchidism at three months adjusted to the birthweight distribution of England and Wales was 1.58%. By comparison, in a very similar study conducted around 1960 the incidence was 0.96%. Hence the cryptorchidism rate had apparently increased by 65% over the two decades, which contrasted with the twofold increase in the national orchidopexy rate. The proportion of boys undergoing orchidopexy appeared consistently to be roughly twice the proportion of boys with an undescended testis at 3 months of age. The increase in cryptorchidism and disparity with the rate of orchidopexy are not easily explained and are the subjects of continuing study.