The prevalence of cryptorchidism in newborn term infants is 2% to 8% worldwide.[2] This decreases to 1% to 2% after the first few months of life, because congenital cryptorchidism may spontaneously resolve with the neonatal peak of testosterone by 3 months.[3] While only a few reliable prospective studies have been conducted to evaluate trends in cryptorchidism incidence, English research has produced some of the most relevant. The first study conducted in the early 1960s reported an incidence of 4.2% at birth and 0.97% at 3 months.[4] A few decades later a second study reported an incidence of 5.01% at birth and 1.78% at 3 months.[5] In a third, more recent study, prevalence was reported as 7.6 per 1000 male live births, with an orchiopexy rate of 1.8 per 1000 males aged 0 to 4 years.[6] There is controversy regarding reports of increasing incidence potentially due to endocrine disruption/environmental exposures, and more studies are needed to prove or disprove this hypothesis.[3][7] Two-thirds of cases are unilateral, while the remainder are bilateral.

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