Maternal and gestational factors affecting the risk of cryptorchidism and inguinal hernia.

Case-control studies of cryptorchidism and inguinal hernia were undertaken on white males born within the cohort of the Collaborative Perinatal Project of the National Institute of Neurological and Communicative Disorders and Stroke. Significantly elevated risks of cryptorchidism were found for low birthweight, for a high maternal Quetelet's index and for oestrogens administered during gestation (R = 2.8). Similarly, in the case of inguinal hernia, significantly increased risk ratios were observed for low birthweight, for gestational use of progestins (RR = 2.1), and for breech labour (RR = 2.3). Because these malformations and testis cancer share many of the same risk factors, a common mechanism for production of these diseases is proposed which is mediated by testicular hypoplasia induced by excess exogenous or endogenous oestrogen in the mother.