Secular changes in the association between advanced maternal age and the risk of low birth weight: a cross-cohort comparison in the UK

Existing studies provide contradictory evidence concerning the association between child well-being and advanced maternal ages. A potential explanation for the lack of consensus are changes over time in the costs and benefits of giving birth at advanced ages. This is the first study that investigates secular changes in the characteristics of older mothers and in the association between advanced maternal age and child health. We use data from four UK cohort studies covering births from 1958-2001, and use low birth weight as a marker for child health. We find that across successive birth cohorts, the negative association between advanced maternal age and low birth weight becomes progressively weaker which is partially explained by secular changes in the characteristics of older mothers. The results suggest that the association between maternal age and child outcomes is tied to a specific population and point in time.