Effects of stage of lactation, nutrient intake, and cultural differences on the composition of human milk were examined during the first 6 mo of lactation in American and Egyptian women. In both population groups zinc levels in milk decreased from 1 to 6 months of lactation. American women supplemented with Zn had higher levels of Zn in their milk than did unsupplemented American or Egyptian women. Concentrations of calcium and magnesium were not significantly different in milk of American and Egyptian women except at month 6 of lactation. Ca levels in milk of both population groups increased from 1 to 2-3 mo of lactation and then decreased at 6 mo; Mg concentrations increased from 1 to 3 mo and then reached a plateau. Similarities in the longitudinal decrease observed in Zn levels of milk in Zn supplemented and unsupplemented subjects suggested physiological regulation.

Functional consequences of marginal maternal vitamin B-6 status for behavior of the neonate and for mother-infant interactions at age 3-6 mo were assessed by a double-blind procedure. In 27 of 70 Egyptian village women studied, vitamin B-6 concentration of their milk was considered indicative of poor maternal vitamin B-6 nutriture. Neonatal behavior, quantified by the Brazelton Neonatal Behavioral Assessment Scale, showed that consolability, appropriate build-up to a crying state, and response to aversive stimuli were significantly correlated with maternal vitamin B-6 nutriture. Naturalistic observational procedures, used twice monthly with infants aged 3-6 mo, indicated that mothers assessed as having marginal vitamin B-6 status were less responsive to their infants' vocalizations, showed less effective intervention to infant distress, and were more likely to use older siblings as care-givers than were mothers of better vitamin status. We conclude that vitamin B-6 was a factor influencing both the behavior of the mother and her infant.

Several potential determinants of birth weight and neonatal behavioral organization, ie, maternal anthropometry, food intake (energy, protein, and plant- and animal-source foods), morbidity, and household socioeconomic status, were followed systematically in a semirural Egyptian population during greater than or equal to 6 mo of pregnancy. In early pregnancy mothers were generally normal weight to moderately overweight. Their mean energy intake, largely from plant sources, was approximately 8.37 MJ/d (2000 kcal/d) during trimesters 2 and 3. Early (3 mo) pregnancy weight and weight gain during trimesters 2 and 3 were significantly positively related to birth weight Z scores. The best predictor model examined for birth weight included early pregnancy weight, weight gain, and length of gestation (R2 = 0.45). Early pregnancy weight and maternal intake of animal-source foods were significant positive predictors of the newborn's orientation and habituation behavior, respectively. Habituation and orientation measures assess the infant's early ability to process information.