Introduction to Preterm Infant Body Composition

Moderate and late preterm infants (MLPTI) constitute a significant portion of neonatal births. However, medical professionals often lack data on their long-term development. A recent study specifically evaluated preterm infant body composition at two years of corrected age. It compared these findings to existing literature on term-born infants while identifying links to early-life growth patterns. The researchers focused on infants born between 32 and 36 weeks of gestation.

Key Findings on Fat and Lean Mass

The study included 80 MLPTI to assess their physical development. Researchers used deuterium-labeled water to determine body composition precisely. The results showed a mean percentage body fat mass of 25.3% and a mean fat-free percentage of 74.7%. Additionally, the mean fat mass index (FMI) was 3.9 kg/m², while the fat-free mass index (FFMI) averaged 11.4 kg/m².

Interestingly, these infants displayed higher fat mass percentages than term-born peers. Furthermore, their FFMI remained relatively low. This suggests that MLPTI may experience an altered preterm infant body composition characterized by reduced muscle or lean mass rather than simple obesity. Consequently, clinicians must distinguish between healthy weight gain and excess fat accumulation during follow-ups.

The Role of Early-Life Growth

Early weight changes significantly influence long-term outcomes. The study found that a 1 SD increase in weight z-score from term-age to three months was associated with a 2.2% higher fat mass at two years. Notably, this association did not extend to the Fat Mass Index. These findings emphasize the importance of monitoring growth trajectories closely during the first few months of life. High-velocity weight gain shortly after birth may lead to higher adiposity later in childhood.

Clinical Implications for Pediatric Practice

Pediatricians should exercise caution regarding rapid weight gain in MLPTI. While catching up is necessary, an imbalance between fat and lean mass can increase metabolic risks. Future research should investigate how specific feeding practices and nutritional interventions can optimize muscle development. Overall, the study highlights the need for tailored nutritional strategies that prioritize fat-free mass accretion.

Frequently Asked Questions

How does the body composition of preterm infants differ at age two?

Moderate and late preterm infants often have higher fat mass percentages and lower fat-free mass indices compared to infants born at full term.

Does early weight gain affect later fat mass?

Yes, significant weight gain between term-age and three months of corrected age is linked to higher body fat percentages at two years.

What are the risks of low fat-free mass in MLPTI?

Low fat-free mass or lean mass may indicate reduced muscle development, which can impact metabolic health and physical strength as the child grows.

Disclaimer: This content is for informational and educational purposes only... Refer to the latest local and national guidelines for clinical practice.

References

Lafeber AH et al. Body composition at 2 years of age in moderate and late preterm infants. J Pediatr Gastroenterol Nutr. 2026 Feb 21. doi: 10.1002/jpn3.70378. PMID: 41721634.

Van de Lagemaat M et al. Growth and body composition of infants born moderate-to-late preterm fed a protein- and mineral-enriched postdischarge formula. Am J Clin Nutr. 2024;120(1):111-120.

Giannì ML et al. Early infancy growth, body composition and type of feeding in late and moderate preterms. Front Pediatr. 2022;10:973161.