<p>The hypothesis that formal childcare stimulates fertility by reconciling work and family life is theoretically well-grounded and mostly tested using national or regional variation in the availability of childcare provisions. However, previous research rarely assesses the relation between individual-level formal childcare uptake and continued childbearing. Consequently, this study applies dynamic propensity score matching and hazard models to unique linked Census and register-data for the complete residential Belgian population for 2011–2014 to estimate the effect of formal childcare uptake on second birth hazards amongst 58,675 working mothers with a young firstborn child in 2011. Results suggest strong patterns of self-selection of mothers into formal childcare uptake, implying that profiles that typically use formal childcare are more likely to progress to a second birth, regardless of the effect of their uptake of formal childcare for the firstborn child. With respect to the effect estimations, the study evidences a positive effect of formal childcare uptake on second birth hazards shortly after the first birth, which weakens when controlling for selective formal childcare uptake. Hence this study demonstrates a linkage between actual childcare uptake for the firstborn child and subsequent second births, which is more specific than the wide range of potential mechanisms underlying positive associations between national or regional-level childcare coverage and childbearing. The finding that formal childcare uptake facilitates the transition to a second child in a low fertility context should invite policy-makers to reflect on barriers to formal childcare uptake, and well-documented subgroup inequalities in access to formal childcare.</p>