<p>This paper explores the long-term impact of transitioning to parenthood on the employment trajectories and relative career advancement of mothers and fathers over three decades in the U.S. Using data from the National Longitudinal Survey of Youth 1979 and group-based trajectory modeling, this study identifies distinct patterns in employment and imputed promotion incidence shaped by the first childbirth. An imputed promotion measure based on wage and working-hour increases is developed to address gaps in available data on career progression. The findings highlight pronounced gender disparities: fathers follow fewer, more stable career pathways and sustain higher promotion rates, whereas mothers face more complex and often disrupted career trajectories due to childbearing and caregiving responsibilities. Moreover, within each gender, individual characteristics like race and education are associated with divergent trajectories, shedding light on long-term intra-gender wage inequalities. The findings underscore that the transition to parenthood and career decisions made around the time of first childbirth have long-lasting impacts on within- and cross-gender disparities in the workplace. By studying the interplay of employment and promotions over an extended period for mothers versus fathers, the findings reveal a potential mechanism contributing to earnings disparities.</p>