Summary
Background: Cryptorchidism is one of the most common congenital malformations in males. As male sexual differentiation is critically dependent on normal androgen concentrations, increased exposure to
environmental factors affecting androgen homeostasis during fetal life may cause cryptorchidism. We investigated the relation between cryptorchidism and lifestyle, occupational exposure and the
characteristics of parents and/or the perinatal and delivery characteristics.
Material/Methods: Case-control study conducted among the eligible 96 cases underwent orchiopexy between 1990 and 2003 and 116 controls were enrolled among boy outpatients born in between 1985 and 2001
and who were determined by pediatricians not to have genitourinary malformation. All the cases and controls were surveyed between 1999 and 2003 in Japan.
Results: We found signifi cant positive associations between cryptorchidism and cesarean section (OR=2.19, 95% CI=1.09–4.40), paternal smoking before and during pregnancy (OR=1.87, 95% CI=1.03–3.37 and OR=1.94, 95% CI=1.08–3.50, respectively) and paternal exposure to diesel exhaust before and during pregnancy (OR=2.42, 95% CI=1.06–5.55 and OR=2.35, 95% CI=0.99–5.59, respectively).
Conclusions: We found associations of cryptorchidism with unusual delivery and paternal smoking during pregnancy. These fi ndings suggested that cryptorchidism might be associated with not only genetic factors but also increased parental exposure to environmental factors. In the future, prospective study is needed to do risk assessment accurately in the hormone-dependent stages of pregnancy critical for testicular descent.

Keywords: Cryptorchidism - surgery, Abortion, Spontaneous - epidemiology, Adult, Case-Control Studies, Cryptorchidism - surgery, Educational Status, Female, Humans, Infant, Newborn, Male, Maternal Age, Parents, Pregnancy, Pregnancy Complications - epidemiology, Risk Factors