We explore whether social mobility influences fertility behavior, using multiple comparative layers to better observe structural and individual-level mechanisms at work. We locate this study in Poland and Russia during periods of socialism and capitalism. Applying event-history analysis techniques to longitudinal micro-data, we find evidence of a relationship between mobility and second birth risks for women only. Status enhancement aims seem the most plausible link between mobility and childbearing. The relationship appears moderated by the economic context, which we interpret as being related to differential selection into upward and downward mobility based on labor market opportunities. In general, the suppressing effect of upward mobility on second birth risks was stronger in the poorer economic context of Russia, whereas the increased second birth risks related to downward mobility were heightened in Poland's more prosperous context.