Ethnic differences in the incidence of malformations following migration.

groups compared differ in both these respects. The influence of ethnic origin on incidence seems to be especially profound (Neel, 1958); and in recent years the arrival in Britain of many members of non-indigenous ethnic groups has opened up the possibility of clarifying the relative importance of genotype and environment by studying their offspring. For many generations, the incidence of genetically determined malformations might be expected to remain almost the same as in the country of origin. The pattern of environmentally determined defects, on the other hand, would probably become more like that observed in children of indigenous descent, although this change might not be immediate if cultural factors were responsible for the difference. In this paper, the main immigrant groups in Birmingham are compared with those of similar ethnic origin in other countries, and with the British-born population, in respect of the incidence of malformations among their offspring. Figures for children of mixed parentage are also given; there