Abstract
What to eat during pregnancy has been a topic of interest for centuries. Initially, there were many philosophical beliefs about what pregnant women should eat to avoid "marking" their baby. Observations that poor women tended to have worse pregnancy outcomes than did women with adequate incomes showed that the quality of the mother's diet was linked to the baby's health. Natural experiments, such as severe food deprivation during World War II, further demonstrated the critical role of maternal nutrition in pregnancy outcomes. Shortly thereafter, researchers showed that prepregnancy nutrition also influenced the course of pregnancy with underweight women tending to have poor outcomes. These findings were the foundation for establishing programs providing dietary counseling and food supplements to at-risk pregnant women. The first major program was in Montreal, which became the basis for the US WIC (Women, Infants, and Children) program that started in 1972 and continues to today. Numerous food or nutrient intervention trials were done over the next 40 years demonstrating that providing undernourished women with nutrient-rich foods improved fetal growth. Supplementation with iron, folate, or micronutrient tended to have smaller effects. Looking back over the historical studies of maternal nutrition provides insights for how to move forward. The data suggest that intervening prior to conception, as well as during pregnancy, improves the baby's growth and long-term health especially in underweight or undernourished women. Thus, prenatal nutrition programs should span the woman's reproductive cycle rather than pregnancy alone.