The month of birth does not affect the risk of hypospadias
We studied the pattern of annual cyclical variation of hypospadia by month of birth for all boys born in Denmark after 1983 and hospitalized with hypospadias. We found little indication of any seasonal pattern, with a peak to low ratio of 1.06 (95% CI: 1.00-1.17)
Skriver, M. V., Pedersen, L., Stang, P., Lund, L., Rothman, K., & Sorensen, H. T. (2004). The month of birth does not affect the risk of hypospadias. European Journal of Epidemiology, 19(12), 1135-1136.