Research on reconciling family and employment debates if maternal part-time employment works as ‘stepping stone’ to full-time employment or as gateway to a long-term ‘mommy track’. We analyse how mothers’ transition from part-time to full-time employment is shaped by changing reconciliation legislations and how this is moderated by reconciliation-relevant factors like individual behaviours and macro conditions. We extend the literature on work–family reconciliation by investigating mothers’ employment behaviour after the birth of their last child, i.e., after the family formative phase. We draw upon Germany with its considerable regional and historical heterogeneity. Using event history methods on SOEP-data, we observe mothers who (re)enter part-time employment (i.e., up to 30 weekly working hours) after their last childbirth. Results suggest that the impact of reconciliation legislations depends on the moderation by other factors. Recent reconciliation-friendly legislations may have contributed to the polarization of maternal employment patterns: more and less employment-oriented mothers diverge sooner after childbirth than before. Legislations co-occur with increases both in childcare institutions and part-time culture, but their moderation effects compete. Hence, boosting part-time work as either a ‘stepping stone’ or a ‘mommy track’ requires a deep understanding of the mechanisms behind legislations as well as more explicit policy incentives.