["Economics of Transition and Institutional Change, Volume 34, Issue 2, Page 339-358, April 2026. ", "\nABSTRACT\nThis study investigates the causal effect of fertility on female labour market outcomes in East and West Germany. We use twin births as an exogenous variation for family size. Our results suggest a negative relationship between the number of children and maternal labour market outcomes. However, this connection is significantly stronger in West Germany than in East Germany for the second and third child. By the fourth child, the effects in the two parts of the country become more similar. Further subgroup analyses suggest that these differences can be explained by regional institutional conditions, such as the availability of public childcare facilities, and to a lesser extent by attitudes towards working mothers.\n"]