While formal childcare facilities or ECEC (i.e., mainly daycare centers and childminders) are very effective levers for reducing developmental inequalities present in early childhood, these facilities are themselves marked by strong inequalities in access. The reasons for the under-representation of disadvantaged families have already been studied, but not in a systematic way. The review work presented in this thesis made it possible to 1) construct an integrative model of barriers to access to formal childcare for these populations and 2) evaluate this model through a PRISMA systematic review and meta-analysis of the literature. socio-structural barriers are the only ones targeted by current public policies. However, our review shows that psychological barriers, which have never been theorized before, are at least as important as these socio-structural barriers. New public policies should be created to act on psychological barriers, otherwise, the effectiveness of structural reforms could be severely limited.