Congenital clubfoot. Month of conception.

The medical records of 330 children who were born with uncomplicated congenital clubfoot were reviewed retrospectively. To determine their months of conception, the duration of gestation was extrapolated and those which were less than 40 weeks were noted. The years of conception for the studied children were from 1956 to 1994. Months of the year were ascribed angle values and the distribution of conceptions per month were grouped in radial manner. Using a circular analysis for variance a lack of uniform circular distribution was found for the grouped months of conception. There is a significant seasonal variation in the data. The mean month of conception was June. This finding is at variance with the peak months of conception for the population of the United States for the years 1989 through 1993. The theory that congenital clubfoot is caused by an intrauterine Enterovirus may be supported by this data. The summer and fall peak of Enterovirus infections in temperate climates coincide with the stage of embryologic development (> 8 weeks) which would allow an anterior horn cell lesion to lead to a deformity such as congenital club foot.