334 - Beyond Weight: Challenges in Defining Growth Failure in Very Low Birth Weight Infants

Publication Number: 3322.334

Julieta M. Conti, University of British Columbia Faculty of Medicine, Vancouver, BC, Canada; Susan G. Albersheim, University of British Columbia, Vancouver, BC, Canada; Ye Shen, BC Children's Hospital Research Institute, Vancouver, BC, Canada; Rajavel Elango, University of British Columbia Faculty of Medicine, Vancouver, BC, Canada

Background: Premature infants, particularly those with very low birth weight (VLBW), have high metabolic demands and are at risk for postnatal growth failure. As survival rates improve among extremely preterm infants, optimizing nutrition and growth is critical. However, wide variation in how growth failure is defined makes comparison across studies challenging and may mask the true extent of growth restriction.

Objective: 1)To describe growth outcomes based on changes in weight, length, and head circumference Z-scores among VLBW infants admitted to our NICU.
2)To determine the prevalence of optimal growth (Z-score decline < 0.8 from birth to discharge).
3)To identify clinical and demographic factors associated with suboptimal growth.

Design/Methods: This retrospective chart review included infants with birth weight < 1500 g and gestational age < 33 weeks admitted to our Level III centre in 2023. Weight, length, and head circumference were recorded weekly from electronic medical records, and Z-scores calculated using Fenton 2013 charts. Suboptimal growth was defined as Z-score decline >0.8 from birth to discharge (mild 0.8-1.2, moderate 1.2-2.0, severe >2.0). Univariate proportional-odds logistic regression was used to identify associated risk factors.

Results: Final analysis included 110 infants (11 died before discharge). Weekly growth trajectories were plotted using Z score for every infant (Fig 1). Using a Z-score decrease >0.8 in any parameter between birth and discharge, 70.1% (n=76) met criteria for growth failure (Fig 2). When restricted to weight Z-scores alone, prevalence decreased to 49% (n=54). On univariate analysis, growth failure was associated (Fig 3) with retinopathy of prematurity, necrotizing enterocolitis, cholestasis, and metabolic bone disease. Each additional 5 days to reach full enteral feeds increased odds of suboptimal growth by 13% (OR 1.13, 95% CI 1.05-1.23), while longer NPO duration showed a similar but non-significant trend (OR 1.11, 95% CI 0.99-1.25).

Conclusion(s): Despite advancements in neonatal care, growth failure remains strikingly common. Our data show that weight alone may be insufficient to monitor growth in this population, as many more infants were identified after including length and head circumference Z score variations. Our follow-up study will explore barriers and enablers to accurate length and head circumference measurement to strengthen growth assessment practices. Future prospective studies are needed to define nutritional and clinical strategies that optimize growth and long-term outcomes in premature infants.

Fig 1. Z score progression of infants from birth to discharge
This spaghetti plot shows all infants included in this study and their Z score progression throughout their admission.

Fig 2. Prevalence of growth failure in this cohort
This table shows the prevalence of growth failure using two different definitions. For the second column, growth failure is defined as a decrease larger than 0.8 points in Z score for either weight, head circumference or length (using whichever was more severe to classify infants). On the third column, growth failure was defined as a decrease larger than 0.8 points in Z score only for weight. Growth failure was further characterized as mild if the decrease in Z score was between 0.8-1.2, moderate if it was between 1.2-2, and severe if it was larger than 2.

Fig 3. Univariate analysis
Proportional odds logistic regression was performed, using growth failure as outcome (Z score decrease larger than 0.8 points from birth to discharge for either weight, length or head circumference). Results shown as above. ROP: retinopathy of prematurity (any stage), MBD: metabolic bone disease, NEC: necrotizing enterocolitis (stage 2 or greater), BPD: bronchopulmonary dysplasia, IVH: intraventricular hemorrhage (grade 3 or 4)