This paper illuminates processes of cumulative disadvantage and the generation of health inequalities among mothers. It asks whether adverse circumstances early in the life course cumulate as health-harming biographical patterns across the prime working and family caregiving years. It also explores whether broader institutional contexts may moderate the cumulative effects of micro-level processes. An analysis of data from the British National Child Development Study and the US National Longitudinal Survey of Youth reveals several expected social inequalities in health. In addition, the study uncovers new evidence of cumulative disadvantage: Adversities in early life selected women into long-term employment and marriage biographies that then intensified existing health disparities in mid-life. The analysis also shows that this accumulation of disadvantage was more prominent in the US than in Britain.