Abstract
In a preceding report1it was shown that the first four children in a family are less likely to exhibit congenital deformities than are subsequent offspring. Since, of necessity, parents are older when their later children are born, this observation raised the question as to the age of the mother when defective children begin to be born more often than is expected by chance. The present report deals with this question. MATERIALS AND METHODS Five hundred and seventy families form the basis for the report. Each family possessed at least one congenitally malformed child who had died and for whom a death certificate had been filed. The home of each family was visited, and information was secured from the mother or a member of her immediate family concerning the year of her birth and that of each of her children. Information regarding the ages of the mothers at the births