ABSTRACT:The New York trial of prenatal protein supplements by Rush et al., together with the study by Stein et al. of the Dutch Hunger Winter, are reviewed to show the importance of maternal nutrition around the time of conception. Both studies reinforce the view that embryonic hypoplasia and dysplasia early in pregnancy cannot be reversed by good nutrition, or protein supplements, during the last half of pregnancy. The high perinatal casualties in both studies were among populations of women with body weights around the Harvard infertility threshold at the time of conception. The population studied in New York was not short of protein and the supplements caused nutritional imbalance for some patients