Undescended testicles: an epidemiological review.

In a retrospective study the records of 447 boys (median age 5 y, age range 2 wk to 12 y) undergoing orchidopexy in a university hospital paediatric surgical department over a 2-y period were analysed for epidemiological factors related to disturbed testicular descent by comparison with the notes of an equal number of otherwise healthy male trauma patients matched for age. There were higher rates of peripartal asphyxia and intrauterine growth retardation (reflected by lower birthweights in combination with equal gestational age distribution), more complicated deliveries, an increased incidence of congenital malformations and more frequent occurrence of a number of chronic diseases in the families of affected boys. First- and second-born boys were over-represented in the study group. A cyclical pattern for the month of birth is suggested by the data, but this did not reach statistical significance. Neither was any statistical difference found for premature delivery, the incidence of extra-uterine fertilization, hormonal treatment of the mother while pregnant, twin pregnancies, threatened or imminent abortions or parental age. The literature dealing with this topic was reviewed. Discrepancies between different studies can be explained, at least in part, by considering different forms of undescended testicles as different nosological entities that should be assessed separately in forthcoming research.