This paper estimates the effects of motherhood timing on female career path, using national panel data from the NLSY79, and biological fertility shocks as instrumental variables for the age at which a woman bears her first child. Motherhood delay leads to a substantial increase in career earnings, a smaller increase in wage rates, and an increase in career hours worked. The postponement wage premium is largest for college-educated women, and those in professional, managerial, and clerical occupations.Family leave laws do not significantly influence the premium. Conversely, using measured aptitude level as an instrumental variable for expected future earnings, we show that higher expected career earnings lead women to postpone childbearing.1