Background This study characterises first-year growth patterns in a historical preterm infant cohort, and investigates associated early-life factors and 1-year anthropometry. Methods We analysed 322 South African preterm infants’ (mean 32.8 ± 2.4 weeks gestation) 1-year clinic records after kangaroo mother care discharge. Latent class trajectory modelling identified patterns of weight-for-age (WAZ), length-for-age (LAZ), weight-for-length (WLZ), and head circumference-for-age (HCZ) z-scores (Fenton 2013 Growth Chart; WHO Growth Standards, age-corrected). Z-score patterns were characterised as maintenance, faltering (progressively decreasing), gain (progressively increasing) or catch-up (rapidly increasing, exceeding birth z-score). Ordinal regression analysis investigated associations of early-life maternal/infant factors, birth weight, and early (until 50 weeks postmenstrual age) WAZ gain with growth patterns. One-year stunting (LAZ < -2), wasting (WLZ < -2) and overweight (body mass index-for-age z-score > +2) were compared. Results Best-fit models identified three WAZ and LAZ patterns (gradual gain, faltering, catch-up), three WLZ patterns (maintenance, faltering, catch-up) and two HCZ patterns (maintenance, gain). Most infants displayed maintenance, gradual gain or catch-up. Lower birth weight z-score (BWZ) was associated with LAZ catch-up (OR:8.33 (3.13–20.00)), WLZ faltering (OR:2.94 (1.69–5.00)) HCZ gain (OR:1.92 (1.23–3.13)), but lower 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 gains were associated with 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)), and LAZ faltering (OR:1.39 (1.09–1.75)). WAZ and WLZ faltering were both associated (p < 0.001) with 1-year stunting (45.5%, 23.5%) and wasting (21.8%, 10.3%). Conclusions Most preterm infants had appropriate first-year growth. Lower BWZ was associated with WAZ and LAZ catch-up but WLZ faltering, and sub-optimal early WAZ growth with growth faltering.

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