Maternal and other factors of cryptorchidism--a case-control study in Japan.

A case-control study of cryptorchidism was undertaken in Japan. A hundred and eight mothers of children with cryptorchidism and mothers of their matched controls were surveyed. After 4 pairs which consisted of one of twin siblings either in the cases or the controls were excluded, 104 paired data of singletons were analyzed. As a result, a significantly smaller proportion of the case mothers had suffered from vomiting during the index pregnancy than that of the control mothers (odds ratio, or OR = 0.50, 95% confidence interval, or CI 0.28-0.89). A significantly larger proportion of the case mothers had delivered the index child by vacuum or breech extraction, or Caesarean section than that of the control mothers (OR = 2.09, 95% CI 1.01-3.98). A significantly larger proportion of the case mothers had never breast-fed the index child than that of the control mothers (OR = 3.50, 95% CI 1.20-10.21). Significantly larger proportions of the cases had inguinal hernia (OR = 9.00, 95% CI 1.29-62.97), or congenital cardiac diseases (OR = 8/0, p < 0.05) than those of the controls. It was inferred that endogenous hormonal milieu of a mother, rather than exogenous hormones, might be associated with the occurrence of cryptorchidism.