Association of early postnatal growth trajectory with body composition in term low birth weight infants.

Growth acceleration or catch-up growth (CUG) in early infancy is a plausible risk factor for later obesity and cardiovascular disease. We postulate that this risk may be mediated by an adverse programming of body composition by CUG in early infancy. The study was aimed at evaluating the association between the pattern of gain in weight and length of term low birth weight (LBW) infants from birth to 6 months, with fat mass percent (FM%) at 6 months. Term healthy singleton LBW infants were enrolled. Baby's weight and length z-scores were measured at birth and three follow-up visits. Body composition was measured by dual-energy absorptiometry at last visit. A total of 54 babies (28 boys) were enrolled. The mean birth weight and gestation were 2175±180 g and 37.6±0.6 weeks. Follow-up visits were at 1.4±0.0, 3.0±0.3 and 7.2±0.8 months. The proportion of babies who showed CUG [increase in weight for age z-score (∆WAZ)>0.67] from birth to 1.4, 3.0 and 7.2 months was 29.6, 26.4 and 48.5%, respectively. The mean FM% at 7.2 months was 16.6±7.8%. Infants with greater ∆WAZ from birth to 3 and 7.2 months had significantly greater FM% at 7.2 months after adjusting for current age, size and gender. Infants with early CUG (<1.4 months) had higher FM% than infants with no CUG. We conclude that earlier and greater increment in WAZ is positively associated with FM%.