An extensive body of research shows that motherhood has substantial impacts on women’s earnings, but there is less evidence on the effect of the timing of motherhood, particularly in the long term and from contexts other than the US. This study analyses data from the 1970 British Cohort Study (BCS70) to examine whether the timing of motherhood affects women’s midlife earnings, as well as the role of potential mediators (tertiary education, years in paid work, and number of children). We make use of the occurrence and timing of biological fertility shocks as a source of exogenous variation in the age at first birth. We find evidence for that avoidance of early motherhood may have a positive effect on women’s earnings in midlife in the UK. This effect is likely to be mediated by years in paid work and number of children. These findings call for policies that support early mothers’ employment careers.