• breast-feeding and health;
  • developmental milestones;
  • infant feeding

This study examines maternal reports of the health and attainment of developmental milestones for 1374 breast-fed v. 1414 formula-fed infants. Data were drawn from the 1981 Child Health Supplement to the National Health Interview Survey (NHIS-CHS), a nationally representative sample of some 40 000 households in the United States of America. The results showed smiling to be reported earlier for the infants of breast-feeding mothers. Formula-feeding mothers were quicker to introduce their infants to solid foods, and also reported earlier success in toilet-training their infants than did breast-feeding mothers. Ratings of physical health were comparatively better for the breastfed than for the bottle-fed infants. Although partially accounted for by duration of breast-feeding, demographic factors of low family income and maternal education predicted poorer infant health. These findings suggest that feeding method may modestly influence infant social development and physical well-being.