With proven detrimental impacts on women and their offspring, preventing child marriage is an important aspect of the struggle to reduce global poverty.In this video, CRISTINA BELLÉS-OBRERO analyzes the effectiveness of legislative measures designed to combat child marriage in Mexico since 2014. Taking advantage of the fact that the laws were implemented gradually by the different Mexican states, applying a ‘difference in difference’ model alongside data on births, marriages and school attendance, Bellés-Obrero shows that the reforms had no impact on factors including girls’ educational attainment or the health of their babies at the moment of delivery. Because informal unions offer an attractive alternative to formal marriage in Mexico, the reforms have not had the desired effects. Further research will explore whether the inferior legal status of girls in informal unions compared to their formally married peers actually exacerbates the negative effects associated with child marriage.