Factors associated with infections among breast-fed babies and babies fed proprietary milks.

Correlation of first postnatal year infections among 251 babies was made with the infant feeding mode, socioeconomic status of family, maternal educational level, age, and maternal behavioral factors including smoking habit and number of siblings in the family. Initially, 127 mothers intended to breast-feed and 124 intended to formula-feed their infants. In the correlation matrix maternal education was the highest variable inversely correlated with infection; it was the first to enter in stepwise regression analysis and was highly significant (P less than .0001). Maternal weight gain during pregnancy and infant feeding mode were the next two variables, respectively, to be added during the stepwise regression but they were not significant in the presence of maternal education. The statistical significance of increased maternal education in inverse relation to infection persisted in the presence of the other two factors (P less than .0064). The t test showed no significant difference in the number of infections among the breast-fed and formula-fed babies within any of the three maternal education groups. It may be concluded that in the population studied, the infant feeding mode itself was not significantly related to the number of infections during the infant's first postnatal year when the education of the mother was taken into account.