Mild gestational diabetes as a risk factor for congenital cryptorchidism.

Context: Cryptorchidism is the most common malformation in newborn boys. Maternal diabetes has previously been suggested to be a risk factor for this disorder in one epidemiological study.
Objective: Evaluation of the prevalence of maternal glucose metabolism disorders during pregnancy in newborn boys having normal testicular descent or congenital cryptorchidism.
Design: Postnatal analysis of maternal history concerning glucose metabolism abnormalities during pregnancy among cryptorchid and healthy Finnish boys.
Setting and Participants: The material of this case-control study comprises 1163 boys with normal testicular descent at birth and 125 boys with congenital cryptorchidism. All these singleton Finnish boys were born in Turku University Central Hospital (1997-2001) and were examined at birth and/or at the expected date of delivery.
Main Outcome Measures: Information about maternal diabetes diagnosis and abnormality of the result of a 2-h 75-g oral glucose tolerance test during pregnancy were obtained from the hospital records after delivery.
Results: After adjustment for possible confounding factors, i.e. maternal smoking during pregnancy, maternal age at delivery, and risk factors of cryptorchidism, e.g. prematurity and weight for gestational age, abnormal maternal glucose metabolism was significantly more common in the group of cryptorchid boys [diet-treated gestational diabetes, P = 0.0001; odds ratio, 3.98 (95% confidence interval, 1.97-8.05); diet-treated gestational diabetes or only an abnormal result in oral glucose tolerance test, P = 0.0016; odds ratio, 2.44 (95% confidence interval, 1.40-4.25)] when compared with boys with normal testicular descent.
Conclusions: Mildly abnormal glucose metabolism during pregnancy was associated with an increased risk for congenital cryptorchidism. The mechanism remains to be elucidated.