The reduction of child mortality is one of the most universally accepted Millennium goals. However, a significant debate came out on the means of reaching it and on its realism with regard to the situation of most of the least developed countries. The recommendations made for the achievement of this are mainly medical ones. However, without underestimating the importance of these measures, in particular vaccinations, it seems increasingly obvious that the rate of reduction of child mortality is mainly determined by the evolution of macroeconomic environment. The influence of per capita income level on mortality is frequently underlined. But a given income growth does not have the same effect on child survival whether it is stable or unstable. Indeed, rises and falls of income probably have asymmetrical effects on mortality. The purpose of this analysis is precisely to show how macroeconomic instability influences the evolution of child mortality. The analysis is based on a panel sample of 97 developing countries over the period 1980-1999. The effect of exogenous shocks is first examined through a variable of income instability. The study of the relation is then deepened with "primary stabilities": instability of world agricultural commodity prices, instability of exports of good and services and instability of agricultural production.