In firstborn children, risk of diabetes is not associated with a mother's age, but among second or later born children there is a positive association, finds a study in this week's BMJ. Clearly the relation between a mother's age, birth order, and risk of diabetes is more complex than previously thought, say the authors.
All live births in Norway between 1974 and 1998 (1.4 million people) were followed for a maximum of 15 years and were linked to cases of type 1 diabetes diagnosed between 1989 and 1998.
There was no association between a mother's age at delivery and diabetes among firstborn children. However, among fourthborn children, there was a 43% increase in incidence of diabetes for each five-year increase in maternal age.
Various sociodemographic and biological factors may explain this effect, say the authors, but our findings indicate that the relation between maternal age, birth order, and risk of diabetes is more complex than previously thought, they conclude.