The Paper of the Month for July is 'Body composition from birth to 6 months in term small for gestational age Indian infants: Effect of catch-up growth' The blog is written by author Vandana Jain. The paper is published in the British Journal of Nutrition and is free to access for one month.
Catch-up growth, i.e., accelerated gain in weight and length to attain a size in accordance with the genetic potential is a common phenomenon in infants who are born at full term with low birth weight (mostly as a consequence of intrauterine growth restriction). Previous studies have indicated that rapid growth during infancy may be associated with greater adiposity and adverse metabolic consequences in later life. It has been suggested that Barker’s hypothesis (i.e., higher risk of diabetes and cardiovascular disease in those born with low birth weight) may be mediated by the greater infancy weight gain, rather than the low birth weight per se. However, there is paucity of direct measurements of fat and fat-free components of weight gain during the dynamic period of early infancy growth in term SGA newborns.
The objective of our prospective observational study was to assess the growth and body
composition of term small for gestational age (SGA) Indian infants from birth to 6 months and evaluate the effect of catch-up growth (CUG) on body composition. Term SGA newborns were recruited at birth from two hospitals in New Delhi; their anthropometry and body composition were evaluated at 3 days, 6, 10 and 14 weeks, and 6 months. CUG was defined as an increase in weight Z-score by >0.67 between two time points. Fat and fat-free mass (FM and FFM) were compared between infants with and without CUG by air displacement plethysmography (PEAPOD).
143 SGA newborns (66 boys) with birth weight of 2336 ± 214 g, and length of 47±1.4 cm were enrolled; of which 109 were followed-up till 6 months; 65% of the infants were exclusively breastfed till 5 months of age, while others were on mixed feeding. The mean height and BMI of the mothers were 155±5 cm, and 21±3 Kg/m2, and a majority belonged to lower or low-middle socioeconomic strata. Median weight Z-score of the infants (calculated using WHO reference data) increased from -2.3 at birth to -1.3 at 6 months, while median length Z-scores increased from -1.4 to -0.9, indicating a significant erasure of growth deficits by 6 months of age. Mean FM% increased more than four-fold from 5.5% at birth to 23.4% at 14 weeks, with subsequent plateauing. CUG was seen in 52% of the infants by 6 months of age; lower birth weight, exclusive breastfeeding and higher parental stature were the main determinants. At 6 months, infants with CUG had higher fat mass (1796 ± 491g vs. 1196 ± 474 g, p<0.001), and similar fat-free mass (4969 ± 508g vs. 4870 ± 622g, p=0.380). Of the approximately 700 g higher weight in those with CUG (6796 ± 666 g vs. 6057 ± 751g), nearly 600g was composed of fat. FM% was 26.5 ± 5.8 vs. 19.7 ± 6.9, p<0.001 in those with and without CUG. The higher the weight gain between 0-6 mo, higher was the FM%. Follow-up of this cohort will provide insight into the long-term effect of disproportionate gain in FM in early infancy in SGA babies.