We explore whether differences in intergenerational income mobility between the UK and Sweden show up early in life, finding stronger associations between parental income and birthweight, height and school performance in the UK. We investigate whether these differentials can account for the country difference in income mobility. While differences in the associations in birthweight and height are too weak to matter, school performance does account for a substantial part of this difference. However, country differences in the earnings returns to these skills are at least as important as the differences in the link between parental income and skills.