Anencephalus in Canada 1943–1970

Elwood, J. M. (Univ. of Ottawa. Royal Ottawa Hospital. Ottawa K1Z 7K4 Canada). Anencephalus in Canada 1943–1970. Am J Epidemiol 100:288–296, 1974.—A retrospective study of the mortality (stillbirths and deaths) from anencephalus in Canada from 1943 to 1970 is presented. Mortality rates may underestimate incidence by up to 10 to 15%. The annual mortality rate has fallen from 1.6 to 0.8/1000 total births over this period; provincial mean rates range from 2.1 (Prince Edward Island) to 0.7 (British Columbia). The time trends differ in different areas; the rates in British Columbia have been stable while those in Ontario have shown the greatest fall, from over 2.3/1000 in the 1940's to 0.8 in 1970. The trend in Ontario is similar to the decline in incidence reported from New England. A peak in mortality in the 1949–1952 period is seen. There has been a slight increase in the male proportion of anencephalus deaths, and a large increase in the proportion certified as infant deaths rather than stillbirths. These findings are discussed in relation to current etiologic hypotheses.