First-year growth trajectories of preterm infants receiving kangaroo mother care, their early life predictors and association with one-year malnutrition

Abstract

Background Longitudinal growth of South African preterm infants is inadequately described. This study characterises first-year growth trajectories in a historical preterm infant cohort, and investigates associations with early-life predictors and one-year anthropometry. Methods Clinic records of 322 preterm infants followed up for one year post-discharge from a South African tertiary hospital’s kangaroo mother care unit were analysed. Latent class trajectory modelling identified characteristic trajectories of weight-for-age (WAZ), length-for-age (LAZ), weight-for-length (WLZ), and head circumference-for-age (HCZ) z-scores, calculated using Fenton Growth Chart and WHO Growth Standards (age-corrected). Ordinal regression analysis determined odds ratios (ORs) for early life predictors (maternal/infant factors, birth weight, early WAZ gain) of growth trajectories. One-year underweight (WAZ<-2), stunting (LAZ<-2), wasting (WLZ<-2) and overweight (BMI-for-age z-score > + 2) were compared using Chi-squared/Fisher’s Exact tests. Results Best-fit models identified three WAZ and LAZ trajectories (faltering, gradual gain, catch-up), two WLZ trajectories (faltering, gain) and two HCZ trajectories (maintenance, gain). Lower birth weight z-score (BWZ) predicted LAZ catch-up (OR:8.33(3.13-20.00)), WLZ faltering (OR:1.69(1.11–2.70)) and HCZ gain (OR:1.92 (1.23–3.13)), but lowered odds of gradual WAZ gain (OR:0.36(0.19–0.68)) and WAZ faltering (OR:0.56(0.34–0.92)). Smaller early WAZ gain predicted gradual WAZ gain (OR:2.27(1.56–3.33)), WAZ faltering (OR:1.47(1.11,1.96)), LAZ catch-up (OR:1.85(1.25–2.70)), LAZ faltering (OR:1.39(1.09–1.75)). WAZ and WLZ faltering respectively resulted in more underweight (49.1%, 22.4%), stunting (45.5%, 23.5%) and wasting (21.8%, 10.3%), while gradual LAZ gain resulted in least underweight (2.0%), stunting (2.1%) and wasting (2.1%, all p < 0.001). Conclusions Preterm infants display various first-year growth trajectories. Lower BWZ predicted catch-up growth, while poor early WAZ growth predicted growth faltering.