Between 1990 and 2010 child mortality decreased in general terms in the Least Developed Countries (LDCs), although the differences between countries over time are significant. This paper examines the relationship between short-term economic fluctuations and changes in child mortality in the LDCs during the period 1990-2010. Unlike other studies, we consider a large group of LDCs and provide empirical evidence of the asymmetrical effects of variations in Gross Domestic Product per capita on the evolution of child mortality rate in periods of economic recession and expansion. The significance of said effects diminishes when other relevant socio-economic control variables are considered, and some development policy considerations are addressed in order to achieve the Millennium Development Goal 4 target