Feeding Method, Nicotine Exposure, and Growth during Infancy

Abstract

ObjectiveTo answer three questions: 1) Are infants breastfed by smokers at risk of rapid weight and length gain? 2) Is rapid growth during infancy partially attributable to ingestion of smokers’ breastmilk? 3) If so, what are the implications for breastfeeding by smokers? Study DesignUsing data from the Norwegian Mother, Father and Child Cohort Study and Medical Birth Registry of Norway (N=54,522) we examined changes in weight, length, weight-for-length z-score (WFLZ) during infancy in the context of maternal smoking (0, 1-10, >10 cigarettes/day) and feeding method during the first 6 months (breastfed, formula-fed, mixed-fed). We fit generalized linear models, adding a smoking by feeding method interaction term to evaluate the effect of ingesting smokers’ breastmilk. ResultsBreastfed infants of both light and heavy smokers experienced WFLZ gains of 0.05 (95% CI: 0.01, 0.09), and 0.13(95% CI: 0.07, 0.18) respectively. Among mixed-fed infants, only heavy maternal smoking predicted WFLZ gain (0.10; 95% CI: 0.05, 0.16). Among exclusively formula-fed infants maternal smoking did not predict rapid growth. Interaction models suggest that infants ever-breastfed (i.e., breastfed and mixed-fed groups combined) by heavy smokers gained weight (100 grams; 95%CI: 30, 231) and length (2.8 mm; 95%CI:0.1, 5.6) attributable to ingesting smoker’s breastmilk. ConclusionsInfants breastfed by smokers experience rapid growth, some of these gains are attributable to ingesting smokers’ breastmilk. Among infants breasted by light smokers, these gains are within the range of normative growth patterns for healthy, breastfed infants.