Social inequality in fetal growth: a comparative study of Denmark, Finland, Norway and Sweden in the period 1981-2000

Objective: To examine the socioeconomic patterns and time trends in fetal growth in Denmark, Finland, Norway, and Sweden from 1981 to 2000. Design and settings: Data on all live-born singleton births was drawn from national population registries in each of the four countries (Denmark n = 1 077 584; Finland n = 400 442; Norway n = 929 458; Sweden n = 1 761 562). Main outcome measure: Slope index of inequality (SII) and mean differences in birthweight for gestational age, SII and risk differences in small-for-gestational-age (SGA) and large-for-gestational-age (LGA) infants. Results: In all countries, gradients in fetal growth by parental education existed. Low parental education was associated with lower birthweight, increased risk of SGA and decreased risk of LGA. Mother's education exerted the strongest influence on outcomes, whereas father's education had a weaker effect. The educational gradients as measured by the SII were generally steepest in Denmark, followed by Norway, Sweden, and Finland. From 1981 to 2000, the educational gradients in birthweight decreased in all countries, except Denmark where it increased. All countries experienced small decreases in the educational gradient in SGA over time. Conclusion: The economic recession in Denmark in the 1980s was concurrent with an increase in disparities in fetal growth, whereas the economic recession in Finland and Sweden in the early 1990s did not substantially increase the socioeconomic inequality in fetal growth. The economic growth in the later part of the 1990s may have diminished the socioeconomic inequality in fetal growth in Finland, Norway, and Sweden.