The role of maternal body composition on infant body composition in the postpartum period
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Currently, about 1 in 3 women of reproductive age are obese (Flegal, Kruszon-Moran, Carroll, Fryar, & Ogden, 2016). Obesity in pregnancy has been associated with adverse maternal and infant outcomes (“Clinical Management Guidelines for Obstetrician–Gynecologists. Number 49, December 2003,” 2003) and maternal overweight and obesity have been implicated as increasing the risk for early childhood obesity (Ramonienė et al., 2017). Obesity is defined by the World Health Organization as having a body mass index (BMI) greater than 30 kg/m2, however, there is mounting evidence that BMI is not an accurate measure of adiposity (Kennedy, Shea, & Sun, 2009), which is one of the leading clinical concerns surrounding obesity. Understanding the associations between maternal body composition and infant body composition could begin to answer questions regarding the underpinnings of intergenerational obesity and offer a modifiable factor such as body composition as a target of opportunity to improve maternal and infant outcomes. This secondary analysis of 372 mother-infant dyads examines the associations of maternal body composition, as measured by BMI, fat mass and lean mass, with infant body composition, as measured by fat mass, lean mass, and BMI z-scores. Fat and lean masses were derived from dual-energy x-ray absorptiometry (DXA). Correlations between maternal BMI and maternal fat and lean mass were explored at one month postpartum. Associations between maternal body composition exposures at one month postpartum and infant body composition outcomes at one, four, and seven months postpartum were explored in the entire cohort and then stratified in two separate analyses by maternal BMI and infant sex to determine the potential for effect modification. Maternal BMI was strongly correlated with maternal fat mass at one month postpartum (r=0.91), and less strongly correlated with maternal lean mass (r=0.71). Maternal lean mass was positively associated with infant lean mass at four months postpartum. In obese women, maternal BMI was negatively associated with infant lean mass at seven months postpartum. In overweight women, maternal fat mass and maternal lean mass were positively associated with infant lean mass. In obese women, maternal fat mass was negatively associated with infant lean mass at four months postpartum. Maternal fat mass and lean mass were positively associated with infant lean mass at four and seven months postpartum in females but not in male infants. An increase in maternal lean mass was also found to be associated with a significant increase in female infant BMI z-scores at seven months postpartum but were not associated with male infants’ BMI z-scores. This study found that obese women with increased adiposity, as measured by BMI and fat mass, tended to have infants with less lean mass at four and seven months postpartum, while overweight women with increased lean mass tended to have infants with greater lean mass at all postpartum through seven months postpartum. It was also found that female infants born to mom’s with larger fat mass or larger lean mass tended to have increased lean mass at four and seven months postpartum, while there seemed to be no associations with maternal and infant body composition in male infants. These results confirm that the first year of life is an important time in infant development and potential programming, but they also suggest that this programming may be associated with lean mass accrual in early infancy as opposed to fat mass or adiposity. The complexity of the relationships between maternal and infant body composition in the postpartum period may involve other factors such as sex differences, genetics and nutrition, and should be further explored in future studies.