How Much Does Birth Weight Matter for Child Health in Developing Countries? Estimates from Siblings and Twins

200 million children globally do not meet their potential for growth, and suffer the consequences in terms of future health, education and earnings. There is a well-established literature on the effects of in utero environment on later health in the US and Europe; however, there is less research on the most at risk populations in developing countries. This paper provides evidence on the effects of birth weight on subsequent health using information on over a million children in 72 countries from the Demographic and Health Surveys. I account for missing data and measurement error using instrumental variables, and also adopt an identification strategy based on sibling and twin models to control for potential omitted variable bias. I find a consistent effect of birth weight on risk of death, stunting, wasting, and coughing, with some evidence for fever, diarrhoea and anaemia. Results imply that focusing solely on reducing mortality, and not on improving infant health more broadly, may be missing the opportunity to build the health capital and life chances of those affected. Investments in the status and health of women are likely to have long run returns in terms of the health and productivity of their children.