[Abnormalities among newborn children born to immigrants in Denmark in the period 1983-1987].

It has recently been discussed whether there was a higher incidence of congenital malformations among newborns of immigrant mothers than among Danish infants. The study is based on information retrieved from two registries in the Danish National Board of Health, both with national coverage: The Medical Birth Register and the Register of Congenital Malformations. All livebirths in Denmark, born to women from Denmark, Scandinavia, Yugoslavia, Turkey, Pakistan, Morocco, Iran and Vietnam in the years 1983-1987, more than 240,000 infants, were included. When comparing the birth prevalence of congenital malformations in the various groups, the observed rate is corrected for maternal age and parity distribution, fathers' occupation (indicating the social position) and county of delivery, as ascertainment varies between hospitals. This part of the analysis did not support the observation of an increased incidence among offspring of immigrant women. A more detailed analysis, based on a multiplicative Poisson-model, compares the three largest groups: Danish, Turkish and Pakistani mothers. Evaluating the influence of maternal age, father's occupation and county of delivery, the result is that the differences observed can, to a large degree, be explained by these three factors, especially the county of delivery. The remaining differences are no larger than can be explained as random. We were thus unable to support the debated observation on a higher incidence of congenital malformations among infants born to immigrant mothers.