Prooxidant effects of maternal smoking and formula in newborn infants

Background: The purpose of this study was to use the breath ethane test to determine if either maternal cigarette smoking, formula, and/or deficiency of the antioxidant nutrients vitamins A and E was associated with oxidant stress in newborn infants. The rationale for this study was: (1) our observation that cigarette smoking was a source of oxidant stress in pregnant women, suggesting that it could be a source of oxidant stress for infants exposed in utero; (2) formula was predicted to be prooxidant compared to colostrum, which contains several compounds with antioxidant activity in vitro; and (3) deficiencies of vitamins A and E have been shown to promote oxidant stress in experimental animals. Methods: Breath ethane, a volatile alkane produced by peroxide of n-3 fatty acids, was utilized as an index of oxidant stress status. Forty-five healthy full-term infants of the women mentioned above were studied at 18-24 h of age, after four to six feedings of breast milk (colostrum) or casein-based infant formula. Relationships between infant breath ethane, maternal smoking, mode of infant nutrition, and serum concentrations of the antioxidant vitamins A and E of infants were examined. Results: The breath ethane of the entire group of infants whose mothers smoked (n=19) was increased compared to values of infants whose mothers did not smoke (n=26): 97+/-16 versus 43+/-9 pmol/kg/min, p <0.03. When infants of mothers who smoked were eliminated from the analysis in order to study effects of nutrition alone, formula appeared to be prooxidant compared to breast milk. Breath ethane of formula-fed infants (n=16) was 62+/-13 versus 13+/-4 pmol/kg/min for breast-fed infants (n=10), p <0.04. For the group as a whole, there was no correlation between infant breath ethane and serum concentrations of vitamins A and E. Conclusions: Exposure to maternal smoking in utero is prooxidant in newborn infants. Formula also has a prooxidant effect compared to colostrum in newborn infants not exposed to maternal smoking in utero. Further investigations will be necessary to explore the clinical consequences of these observations.