Does maternal smoking in pregnancy explain the differences in the body composition trajectory between breastfed and formula-fed infants?

Abstract

Growth patterns are known to differ between breastfed and formula-fed infants, but little is known about the relative impact of maternal smoking in pregnancy vs. feeding mode on growth trajectory in infancy. We conducted a secondary analysis of a trial, the TIGGA trial involving 290 healthy infants, to examine whether smoking in pregnancy modified the association between feeding mode and body composition of infants. Fat mass (FM) and fat free mass (FFM) were estimated at 1, 2, 3, 4, 6 and 12 months of age using bioimpedance spectroscopy. Formula-fed infants (n=190) had a higher mean FFM at four months [mean difference (MD): 160g, 95% CI: 50.4, 269.5g, p<0.05)] and six months (MD: 179g, 95% CI: 41.5, 316.9g, p<0.05) compared with the breast-fed infants (n=100). Subgroup analysis of breastfed vs. formula-fed infants by maternal smoking status in pregnancy showed that there were no differences in the FM and FFM between the breastfed and formula-fed infants whose mothers did not smoke in pregnancy. Formula-fed infants whose mothers smoked in pregnancy were smaller at birth and had a lower FM% and higher FFM% at one month compared with infants of non-smoking mothers regardless of feeding mode, but the differences were not significant at other time points. Adequately powered prospective studies with longitudinal follow up, specifically designed to examine the relationship between maternal smoking in pregnancy, feeding mode and the body composition of infants, are warranted to better understand the relative impact of maternal smoking, feeding practice and the growth trajectory of infants.