Neonatal and postneonatal mortality by maternal education - a population-based study of trends in the Nordic countries, 1981-2000

Background: This study examined changes in the educational gradients in neonatal and postneonatal mortality over a 20-year period in the four largest Nordic countries. Methods: The study populations were all live-born singleton infants with gestational age of at least 22 weeks from 1981 to 2000 (Finland 1987-2000). Information on births and infant deaths from the Medical Birth Registries was linked to information from census statistics. Numbers of eligible live-births were: Denmark 1 179 831, Finland 834 299 (1987-2000), Norway 1 017 168 and Sweden 1 971 645. Differences in mortality between education groups were estimated as risk differences (RD), relative risks (RR) and index of inequality ratio (RII). Results: Overall, rates of infant mortality were in Denmark 5.9 per 1000 live-births, in Finland 4.2 (1987-2000), in Norway 5.3 and in Sweden 4.7. Overall the mortality decreased in all educational groups, and the educational level increased in the study period. The time-trends differed between neonatal and postneonatal death. For neonatal death, both the absolute and relative educational differences decreased in Finland and Sweden, increased in Denmark, whereas in Norway a decrease in absolute differences and a slight increase in relative differences occurred. For postneonatal death, the relative educational differences increased in all countries, whereas the absolute differences decreased. Conclusions: All educational groups experienced a decline in infant mortality during the period under study. Still, the inverse association between maternal education and RR of postneonatal death has become more pronounced in all Nordic countries.