Birth prevalence of malformations in members of different ethnic groups and in the offspring of matings between them, in Birmingham, England.

STUDY OBJECTIVES The aims were: (1) to compare the birth prevalence of malformations in different ethnic groups and (2) to explore the reasons for the ethnic variations found by examining birth prevalence in the offspring of matings between ethnic groups. DESIGN Analysis of data from a register of malformations and register of births. SETTING Birmingham, England. SUBJECTS A total of 432,778 infants (including stillbirths) born in 1960-84. MAIN RESULTS Significant differences (p < 0.01) between ethnic groups were exhibited by the birth prevalence of neural tube defects (NTD), cleft palate, cleft lip, oesophageal atresia/fistula, hypospadias, hip dislocation, clubfoot, polydactyly, and syndactyly. In the offspring of matings between parents of European and Caribbean origin, the birth prevalence of NTD, cleft lip, hypospadias, hip dislocation, polydactyly, and syndactyly seemed more likely to be influenced by the ethnicity of both parents than by that of the mother alone. The reverse was true for the birth prevalence of NTD in subjects with one parent of Irish origin and on of British. CONCLUSIONS Genetic differences may be responsible for Europeans being at lower risk of polydactyly and at higher risk of NTD, cleft lip, hypospadias, hip dislocation, and syndactyly than Caribbeans. Variations in the intrauterine environment are more likely to account for NTD being more common in Irish than in British subjects.