Risk factor patterns for cryptorchidism and hypospadias

To evaluate the hypothesis of a common etiology for cryptorchidism and hypo spadias, we conducted two case control studies nested in a nationwide cohor t in Sweden, using record linkage between the Inpatient and Birth Registrie s. Cases were 2,782 and 1,220 boys operated for cryptorchidism or hypospadi as, respectively. Five matched controls per case were randomly selected. Pr egnancy and perinatal data were prospectively recorded in the Birth Registr y. Data were modeled through conditional logistic regression. Both cryptorc hidism (odds ratio (OR) = 2.22) and hypospadias (OR = 2.75) were positively associated with other congenital malformations and inversely with maternal parity (OR = 0.77 and 0.52, respectively, for parity 4+ compared with prim iparae). There is evidence that being born small-for-gestational-age and be fore the 33rd gestational week have a greater than additive effect with res pect to both cryptorchidism (OR = 6.19 vs 1.72 expected) and hypospadias (O R = 4.39 vs 2.60 expected) compared with non-small-for-gestational-age boys born at term. Hypospadias was positively associated with severe pre eclamp sia (OR = 2.11). We conclude that the etiologies of the two conditions are partly shared.