Optimizing the growth of very-low-birth-weight infants requires targeting both nutritional and nonnutritional modifiable factors specific to stage of hospitalization.

Background: Data on how baseline characteristics, acuity, morbidity, and nutrition work in combination to affect the growth of very-low-birth-weight (VLBW, <1500 g) infants are limited.

Objective: We aimed to determine factors associated with in-hospital weight, length, and head circumference (HC) trajectories of VLBW infants.

Methods: VLBW infants (n = 316) from the GTA-DoMINO trial were included. Linear mixed-effects models assessed relations of baseline characteristics, acuity (at birth, across hospitalization), major morbidities, and nutrition (enteral feeding type, macronutrient/energy intakes) with changes in anthropometrics over hospitalization (days 1-8, 9-29, 30-75).

Results: Specific factors and the strength of their associations with growth depended on in-hospital time interval. Small-for-gestational-age infants experienced weight gain (4.3   g · kg-1 · d-1; 95% CI: 2.0, 6.5   g · kg-1 · d-1) during days 1-8, versus weight loss (-4.6     g · kg-1 · d-1; 95% CI: -5.6, -3.7     g · kg-1 · d-1) among appropriate-for-gestational-age infants (P < 0.001). Positive-pressure ventilation (versus oxygen/room air) was associated with slower weight (-1.8    g · kg-1 · d-1) and HC (-0.25 cm/wk) gain during days 9-29 (P < 0.001). Morbidities were negatively associated with growth after days 1-8, with patent ductus arteriosus (PDA) showing negative associations with weight (-2.7     g · kg-1 · d-1), length (-0.11 cm/wk), and HC (-0.21 cm/wk) gain during days 9-29 (P < 0.001). Macronutrient/energy intakes were associated with weight across hospitalization (P ≤ 0.01), with greater weight gain (1.3-3.0 g  ·  kg-1  ·  d-1) among infants achieving macronutrient/energy recommendations during days 9-29 and 30-75. Macronutrient/energy intakes were associated with HC during the first month (P = 0.013-0.003), with greater HC gain (0.07-0.12 cm/wk) among infants achieving protein, lipid, and energy recommendations during days 9-29.

Conclusions: Baseline characteristics, acuity, morbidity, and nutrition factors were independently associated with VLBW infant growth. A focus on achieving macronutrient/energy recommendations and improving nutrient delivery to PDA-diagnosed infants may yield improvements to their growth. This trial was registered at www.isrctn.com as ISRCTN35317141.