720 - Preterm and Growth-Restricted Infants in the NICU: Factors Associated With Persistent Growth Failure Through 24 Months Corrected Age

Publication Number: 2702.720

Olivia L. Cole, Medical College of Wisconsin, Arlington Heights, IL, United States; T. Hang Nghiem-Rao, Medical College of Wisconsin, Milwaukee, WI, United States; Brittani Clark, Children's Hospital of Wisconsin, Milwaukee, WI, United States; Katherine Carlton, Medical College of Wisconsin, Mequon, WI, United States; Alicia Sprecher, Medical College of Wisconsin, Milwaukee, WI, United States

Background: Growth failure in preterm infants is common in the neonatal intensive care unit (NICU); however, the trajectory of post-NICU discharge growth is less understood. It remains unclear how discharge growth failure contributes to persistent growth deficits.

Objective: Our aim was to characterize preterm infant growth trajectories from birth to 24 months corrected age (CA) and identify factors associated with growth failure.

Design/Methods: This was a retrospective cohort study of infants admitted to a Level IV NICU between January 2021 and November 2024. Inclusion criteria were a birth gestational age (GA) < 32 weeks or birth weight < 1500 g. Infants with transfer or death prior to NICU discharge, admission after 30 days of life, or congenital anomalies were excluded. Clinical data and growth parameters (weight, length, head circumference (HC), and the respective z-scores) were obtained from hospital, high-risk follow-up, and primary care clinic records at birth, NICU discharge, and CA of 6, 12, 18, and 24 months. Sex-specific Fenton 2013 Preterm growth charts were used for growth parameters at birth and discharge and WHO Child Growth Standards (0-2 years, CA) for all subsequent time points. Growth faltering, the absence of catch-up growth, was defined at 24 months as a z-score < -2. Growth failure was defined as a negative change in z-score: none (≤0.8), mild (>0.8 to 1.2), moderate (>1.2 to 2), or severe (>2) between birth and subsequent time points. Kruskal-Wallis and chi-square tests were used to compare clinical variables between growth failure groups.

Results: After exclusions, 408 infants comprised the final cohort. Mean z-scores were lowest at birth for HC (-0.27) and lowest at discharge for weight (-0.96) and length (-1.37) (Fig 1). Growth faltering was observed for weight in 7%, length in 12%, and HC in 10% of infants at 24 months. Growth failure at 24 months was more common and seen in 24%, 31%, and 25% of infants for weight, length, and HC, respectively. Growth failure was severe for weight in 5% and length in 9% (Fig 2). Infants with growth failure at NICU discharge were born with lower GA, more often female, non-white, and discharged with more prescribed medications. Of these factors, only GA was significantly associated with growth failure at 24 months (Table 1).

Conclusion(s): Although most preterm infants experience catch-up growth post-discharge, approximately one-fourth continue to have growth failure at 24 months. Linear growth appears most affected. Further research is needed to identify potentially modifiable factors associated with growth faltering and long-term growth failure.

Anthropometric Z-Scores by Corrected Age in Months
Mean z-scores are shown with 95% confidence intervals.
A) Weight z-scores were lowest at discharge (-0.96 [-1.09, -0.82]) but showed sufficient catch-up growth by 24 months (-0.26 [-0.42, -0.09]).
B) Length z-scores were lowest at discharge (-1.37, [-1.54, -1.21]) with sufficient catch-up growth by 24 months (-0.67 [-0.84, -0.50]).
C) Head circumference (HC) z-scores were lowest at birth (-0.27 [-0.44, -0.11]) and 24 months (-0.25 [-0.44, -0.06]), indicating maintained growth within the reference range.

Across all growth parameters, there was sufficient catch-up growth, with HC being the most stable.


Growth Failure Severity by Change in Z-Scores (Relative to Birth) Through 24 Months Corrected Age
A) Change in Weight Z-Score: Severe (n = 34) and moderate (n = 62) growth failure were most common from discharge to 6 months CA, while mild (n = 106) growth failure was most frequent from birth to discharge.
B) Change in Length Z-Score: Severe (n = 47), moderate (n = 111), and mild (n = 81) growth failure were most common from birth to discharge.
C) Change in Head Circumference Z-Score: Severe (n = 19) growth failure was most common from discharge to 6 months CA, while moderate (n = 44) and mild (n = 50) growth failure were most prominent from birth to discharge.

Growth Failure Severity and Associated Perinatal and Demographic Factors Through 24 Months Corrected Age
Abbreviations: GA, gestational age; HC, head circumference; CA, corrected age; DC Meds, discharge medications.
Growth failure severity (no, mild, moderate, and severe) was compared across perinatal and demographic factors using Kruskal-Wallis and chi-square tests. Infants with growth failure at 24 months CA were born more premature, more often female, non-White, and discharged on more medications, indicating associations between early GA, sex, race, and discharge medical complexity with long-term growth outcomes.