Background Growth of preterm infants should follow intrauterine rates. Postnatal loss of extracellular fluid shifts growth trajectories to a percentile below that in-utero. Which ‘new’ trajectory a preterm infant should adjust to after completed postnatal adaptation is unknown.

Objective 1) To develop a model for postnatal growth trajectories of preterm infants by characterising growth of such infants which required only minimal postnatal support; 2) to predict trajectories for healthy postnatal growth in any given infant.

Methods Inclusion criteria: infants with (A) 30–35 and (B) 24–29 weeks GA, admitted 2008–2012 to participating hospitals. Exclusion criteria: (A)+(B) maternal diabetes/substance use, nosocomial sepsis (positive blood culture until day of life (DoL) 21 (A) nCPAP >3 days, not on full enteral feeds by DoL 10, (B) mechanical ventilation on DoL >3, FiO2≥0.3 within first 21 DoL, NEC >stage 2, IVH >2, PVL. Models to predict body weight trajectories on DoL 14 and 21 were developed.

Results 890 infants were eligible of 6915 meeting inclusion criteria. Infants had maximum weight loss by DoL 5, regained birth weight by DoL 11 and showed stable growth parallel to intrauterine percentiles during DoL 7–21. Surprisingly the new trajectory was independent from GA with a z-score difference from birth of (A) -0.96 ± 0.75 and (B) -0.88 ± 0.67 at DoL14. Linear regression models predicted weight at DoL 14 (R2=0.88) and 21 (R2=0.82).

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Abstract PO-0460 Figure 1

Preterm FFMI increases progressively until 40 weeks, then remains constant over time like terms

Conclusions 1) The study provides robust estimates of ideal postnatal growth trajectories for preterm infants. 2) The impact on long-term outcome using these trajectories for nutritional adjustment needs to be assessed, ideally in an RCT.