Seasonal variation in anencephalus in Canada

A study of the monthly numbers of stillbirths and of deaths due to anencephalus in Canada from 1954 to 1962 showed a weak tendency to a winter excess of affected births. The seasonal trend was more marked in the Prarie provinces and in Quebec than elsewhere; the maximum rate of anencephalus occurrence was in October to December in the Prairies and in British Columbia, and in January to March in other regions.