Abstract
The seasonal distribution of births was studied in 367 boys with congenital anomalies of the urethra examined at the paediatric department of diagnostic radiology at Karolinska Sjukhuset, Stockholm. Of these children, 221 had urethral valves or valve-like mucosal folds in the posterior part of the urethra, 124 had hypospadias, and 46 had various other anomalies. The seasonal distribution of the group with hypospadias differed from those of the other groups and from that of the entire male population of the country. About two thirds of the boys with hypospadias were born in April-September.