Mortality from congenital malformations of the central nervous system in Norway, 1951-65. Life insurance companies' institute for medical statistics at the Oslo city hospitals, report no. 12.

Congenital malformations of the central nervous system have long attracted the interest of statisticians and epidemiologists. Various features of the data, frequently conflicting, have been emphasised. Hewitt (1965) found that the mortality of spina bifida decreased markedly from east to west on the North American continent and suggested the hypothesis that " . .. both the downward time-trend of recent years and the downward geographical trend as one proceeds westward across America are due to greater outbreeding".