This is a review of short- and long-term consequences of low birth weight (LBW) and of some of its determinants. The results of observational studies and of nutritional experiments aimed at clarifying the relationship between maternal nutrition and birth weight are reviewed. Areas for future research are noted.
LBW is a major public health problem in developing countries. LBW is strongly associated with infant, and especially neonatal, mortality, and there is some indication that it is also related to preschool mortality rates (1–4 years). Long-term measures of physical growth, immune response, and mental development are all adversely affected by LBW. The duration and magnitude of these effects appear to be a function of the type and severity of the weight deficit at birth.
Determinants of LBW in developing countries include maternal nutritional status before and during pregnancy, maternal diet, and perhaps exposure to smoke and infection rates during pregnancy. Studies from around the world have demonstrated that dietary intervention during pregnancy is almost always associated with increased birth weights. It is now known that nutritional supplementation interacts with maternal nutritional status; newborns of well-nourished women benefit little, if any, from dietary supplementation of their mothers during pregnancy, whereas newborns of poorly nourished women (thinnest and shortest) show substantial improvements in birth weight. However, when best to begin dietary supplementation during pregnancy remains an unresolved issue.
Many areas are deserving of further research. Long-term studies of the significance of birth weight, particularly in poor countries, are needed. Experiences with dietary interventions during pregnancy in areas where mean birth weights are very low (i.e., at or below 2,800 g) need to be documented. Advances need to be made in the design of locally appropriate dietary interventions for pregnant women and of risk scales capable of identifying those women who are more likely to benefit from these programs. The influence of a number of factors on birth weight needs to be clarified: intrauterine infection, maternal physical activity, lactation during pregnancy, exposure to cooking smoke, and adolescent pregnancy. Finally, the impact of nonnutritional interventions on birth weight needs to be assessed. These include, for example, family planning, medical care, health and nutrition education, and socioeconomic development programs.