This paper explores how the wage and career consequences of motherhood differ by skill and timing. Past work has often found smaller or even negligible effects from childbearing for high-skill women, but we find the opposite. Wage trajectories diverge sharply for high scoring women after, but not before, they have children, while there is little change for low-skill women. It appears that the lifetime costs of childbearing, especially early childbearing, are particularly high for skilled women. These differential costs of childbearing may account for the far greater tendency of high-skill women to delay or avoid childbearing altogether.