Neonatal Period: Body Composition Changes in Breast-Fed Full-Term Newborns

Abstract

Background: Weight loss during initial days of life in healthy infants is known to consist of loss of both body solids and total body water. However, the nature of these body composition changes needs further investigation. Objective: To investigate the nature of changes in body composition that accompany weight loss during the first days of life in healthy term newborns. Methods: Body composition of healthy full-term newborns was assessed using air-displacement plethysmography. Cross-sectional (n = 262) and longitudinal samples (n = 28) were assessed during the first 4 and 5 days after delivery, respectively. Results: In the cross-sectional sample, mean body weight decreased significantly through day 4 (p < 0.001), mean fat mass (FM) and %FM decreased significantly (p = 0.005 and p = 0.031, respectively) by day 3. There was a significant decrease in mean fat-free mass on days 3 and 4 (p = 0.01 and p < 0.001, respectively). In the longitudinal sample, there was a significant decrease in mean body weight, FM and %FM (p < 0.001, p = 0.001, p = 0.013, respectively) by day 4. On day 5 there was a significant increase in mean body weight, FM and %FM (p < 0.001, p = 0.024, p = 0.036, respectively) when compared to day 4. There was no significant difference in mean FM and %FM values between day 1 and day 5. Conclusions: These results indicate that body composition changes are constituted by a reduction in both fat and fat free mass. However, a greater %FM is lost and consequently regained by day 5 when compared to fat-free mass.

An observational cohort study of weight- and length-derived anthropometric indicators with body composition at birth and 5 mo: the Healthy Start study

“…Although the magnitude of association was largest for WFAZ, its ability to discriminate between FM and lean mass was only marginally significant; this is likely because weight gain in growing infants and children is nonspecific, as it captures increases in adiposity and the accrual of lean muscle and bone mass (12)(13)(14). When we directly compared how change in %FM, a measure of relative FM that is complementary to percentage lean mass, correlated with change in all 3 indicators at the same time, we found that change in %FM was most strongly associated with change in BMIZ, particularly among AGA and LGA infants.…”

“…Healthy Start comprises a large, multiethnic population of .1000 motherchild pairs, which improves our ability to generalize our findings. In addition, we were able to examine associations of the derived indicators with body composition at .1 time during infancy, which is critical given that the first few postnatal months are characterized by rapid changes in body composition (12)(13)(14). Limitations of this study include the fact that the analysis was restricted to singletons born at term; thus, results may not be applicable to cases of multiple gestation or preterm infants, although we note that a study conducted among preterm neonates found similar results (16).…”

“…Despite a flurry of investigations that used ADP to characterize patterns of fat and lean mass gain during infancy (12)(13)(14), few studies, to our knowledge, have formally assessed the relation between derived anthropometric indexes and directly measured body composition. So far, only a few small cross-sectional analyses of data from both term and preterm infants reported poor correlations of birth weight, as well as weight-and length-based indexes, with neonatal FM (15)(16)(17).…”

Body composition in late preterm infants according to percentile at birth

“…Full-term newborns were measured on the third day of life (20). Body weight, length, and head circumference were measured according to standard procedures (21).…”

Is body fat percentage a better measure of undernutrition in newborns than birth weight percentiles?

“…Exclusions included neonates with major congenital abnormalities, multiple births, preterm neonates, or admissions to the neonatal intensive care unit for greater than 48 h as illness or invasive monitoring prevented measurement. The greatest loss in BF% occurs on day 3 and therefore to standardize this measurement we included only neonates measured within 48 h of birth (33). The sample size was based on the main study question of estimating the number of neonates with low BF% with a minimum sample size of 384 required to provide a 95% CI ±3%.…”