Prenatal risk factors for cryptorchidism: a record linkage study.

Using data from the Oxford Record Linkage Study (ORLS), we conducted a case-control study to examine prenatal risk factors for cryptorchidism. We identified 1449 boys born during 1970-86 for whom there was a record of an orchidopexy during 1970-87. Up to eight controls were matched to each case on year of birth and hospital or place of delivery. For each boy and his mother we extracted abstracts of maternity and general hospital records from the ORLS. Low birthweight (trend P < 0.001), low social class (trend P < 0.001), breech presentation (relative risk 1.67; 95% confidence interval [CI] 1.16, 2.41), pre-eclampsia (1.17 [1.00, 1.37]), artificial feeding (1.22 [1.04, 1.45]) and episiotomy (1.13 [1.00, 1.27]) were identified as independent risk factors for cryptorchidism. Gestational age was not independently associated with cryptorchidism after adjusting for birthweight (P = 0.33), and this observation suggested that some cryptorchid boys may have suffered from intrauterine growth retardation. Low birthweight, breech presentation and pre-eclampsia may have in common poor placental function and impaired fetal growth, which may be causes of cryptorchidism.