Associations between growth and childhood body composition in very preterm, late preterm and term children.

Aim: To determine how gestational age at birth and postnatal growth relate to body composition in childhood.

Methods: We calculated conditional growth (birth-2 years, 2 years-6 years) and measured body composition at 2 and 6 years using bioelectrical impedance in cohorts of New Zealand children born very preterm (VPT; 23-31 weeks), late preterm (LPT; 35- <37 weeks) and term (≥37 weeks). We explored the relationships between growth and fat mass (FM) index and fat-free mass (FFM) index at 6 years using multivariable linear regression.

Results: Of 1125 children (51% male), 202 were VPT, 114 LPT and 809 Term. Compared to Term, VPT but not LPT were lighter and shorter at 2 and 6 years and had lower FM index and FFM index. The association between weight growth from 2 to 6 years and both FM index and FFM index at 6 years was stronger than for weight growth from birth to 2 years or height growth at any period in all gestational age groups.

Conclusions: Size and body composition at 2 and 6 years are different between infants born VPT, but not LPT, and at term. Later weight growth is more strongly associated with childhood body composition than earlier growth.