Smoking effects on milk's micronutrient content and infant growth

Smoking during pregnancy negatively affects birth weight and during breast-feeding alters volume and duration of lactation. As consequence of both effects, breast fed infants of smoking mothers have lower growth rates, compared to those of non-smoking mothers. In smoking mothers, at the end of pregnancy, there is an inverse association between cadmium content in maternal plasma and zinc content in fetal blood, while their newborns exhibited increased copper and diminished iron concentrations. No information exists on micronutrient content of breast milk of smoking mothers, associated to longitudinal growth. Ten smoking mothers (mean of cigarettes: 7.1) and 22 non-smoker controls and their infants, have been recruited within one month after delivery, at a Public Hospital in Santiago, Chile. Infant's weight, height, tricipital skinfold, arm and head circumferences and mother's weight were registered. Milk volume has been assessed by deuterium dilution and cotinine concentrations by radio-immuno-assay (RIA). No significant differences existed in age and nutritional status, between mothers. Cotinine levels were 50 times higher in smoking mothers (2576±2341 mU/L vs 54±25) and 12 times higher in their infants compared with those of non smokers (121±99 mU/L vs 10±5 mU/L). Birth weight was significantly different (3290±327 g vs 3558±432 g, p=0.01) but not so at 3 months of age (6026±550 g vs 6099±510 g, p=0.8). Infants' height was significantly smaller in smokers' infants at birth and 3 months of age (50±1 cm vs 51±1 cm and 59±1 cm vs 61±2 cm). The evidence so far indicates that infant's height is compromised which could be related to an altered transference of essential micronutrients, due to a lesser amount of breast-milk and micronutrient concentrations. These objectives will be proved in the second year of the Coordinated Research Project. (author)