BIRTH-DEFECTS AND PARENTAL CONSANGUINITY IN NORWAY

The study compares frequencies of birth defects between immigrant grou ps and the rest of the Norwegian population in Norway and estimates th e influence of consanguinity and socioeconomic factors on these freque ncies. The authors studied all 1.56 million births in Norway from 1967 to 1993, Of these, 7,494 children had two Pakistani parents, 84,688 h ad one Norwegian and one immigrant parent, and 25,891 had two immigran t parents from countries other than Pakistan, The risk of birth defect s relative to the Norwegian group was 0.98 (95% confidence interval 0. 92-1.03) in the group with one foreign and one Norwegian parent, 1.39 (95% confidence interval 1.22-1.60) in the group with two Pakistani pa rents, and 1.04 (95% confidence interval 0.95-1.14) in the group with two parents from other foreign countries; 0.1% of the Norwegian and 30 .1% of the Pakistani children had parents who were first cousins. Ther e was no difference in risk between children of nonconsanguineous Paki stani parents and the other groups, The relative risk of birth defects among children whose parents were first cousins was about 2 in all gr oups. Among the Pakistani, 28% of all birth defects could be attribute d to consanguinity. Low paternal educational level was associated with a slightly increased risk in the Norwegian group, while independent e ffects of parental educational levels were not found in any other grou ps.