683 - Developmental Transitions in Intestinal Structural Growth and Nutritional Coupling in Preterm Infants

Publication Number: 1660.683

Saharnaz Talebiyan, Tufts University School of Medicine, Chestnut Hill, MA, United States; Michael Dolinger, Hassenfeld Children's Hospital at NYU Langone, New York, NY, United States; Rachana Singh, Tufts University School of Medicine, Boston, MA, United States; Indrani Bhattacharjee, Tufts University School of Medicine, Boston, MA, United States

Background: Necrotizing enterocolitis (NEC) remains a major cause of morbidity and mortality in preterm infants due to functional and structural gut immaturity. Bowel ultrasound (BUS) enables radiation-free, real-time assessment of intestinal structure. Longitudinal bowel-wall-thickness (BWT) tracking may reveal developmental patterns reflecting gut vulnerability.

Objective: To define gestational-age-specific trajectories of BWT velocity and to examine coupling between intestinal structural growth, feeding exposure, and somatic growth parameters.

Design/Methods: Prospective pilot observational study of infants < 34 weeks' gestation age (GA) admitted to a level III NICU. Serial BUS were obtained every 7-10 days for up to 8 weeks using a standardized four-quadrant protocol. Feeding volumes, caloric intake, and anthropometrics were recorded daily. Analyses stratified infants by GA at birth. The study cohort (n = 14) had mean GA 29.7 ± 3.1 weeks and mean birth weight 1,170 ± 420; 54 % male; 82 % received antenatal steroids. (Table 1)

Results: Mean BWT increased progressively with advancing GA, while BWT velocity peaked between 29-32 weeks before declining, delineating a discrete phase of accelerated intestinal remodeling (Figure 1). A strong association was observed between feeding volume (mL/kg/day) and intestinal growth velocity, but not with caloric density or duration of feeding. Intestinal structural responsiveness to feeding was greatest at 29-30 weeks (r ≈ 0.95, p < 0.01). Importantly, the interaction between somatic growth and intestinal development changed markedly with maturity. In infants < 30 weeks, bowel growth velocity rose in parallel with weight and linear growth, reflecting coordinated systemic and intestinal development. After 31 weeks, this relationship reversed, with greater somatic (weight and head circumference) growth occurring as intestinal wall growth slowed (r ≈ -0.7; Figure 2). This developmental crossover indicates a physiologic transition from rapid structural expansion to functional maturation of the gut, aligning with the gestational window of highest NEC vulnerability.

Conclusion(s): Preterm intestinal structural growth velocity follows a developmentally regulated, feed-responsive trajectory that peaks between 29-32 weeks. The subsequent decoupling of bowel, feeding, and somatic growth marks a maturational transition coinciding with the clinically well-known NEC-risk window. GA specific monitoring of BWT velocity may offer a physiologic framework for understanding intestinal maturation and serve as an initial step toward precision-based monitoring and prediction of gut health and NEC risk.

Demographic and Clinical Characteristics of the Study Cohort.
Baseline characteristic of preterm infants included in the study.

Intestinal structural growth across development.
Mean bowel-wall-thickness (BWT) velocity (mm/day; blue, left axis) and absolute BWT (mm; orange, right axis) are plotted by gestational-age group. BWT velocity peaks at 29-32 weeks, then declines despite progressive wall thickening. Shaded region (28-33 weeks) denotes the developmental window of heightened intestinal vulnerability.

Developmental modulation of gut-body growth coupling
Correlation coefficients between BWT velocity and somatic growth velocities (weight, length, head circumference) are shown by gestational-age group. Positive coupling in very preterm infants ( < 30 weeks) reverses after 31 weeks, marking a maturational inflection where intestinal structural growth decouples from systemic growth, temporally aligning with the NEC-susceptibility window.