Association between body composition at term equivalent age and Bayley scores at 2 years in preterm infants

A Narrative Review of Strategies to Optimize Nutrition, Feeding, and Growth among Preterm-Born Infants: Implications for Practice

Preterm birth is the leading cause of neonatal and under-5 mortality globally, and healthcare-related burden and nutrition-related morbidities are unsustainable, particularly in resource-limited regions. Additionally, preterm infants are susceptible to multiple adverse outcomes including growth faltering, suboptimal neurodevelopment, and multisystemic morbidities. Maturation, healing, repair, and restoration to normalcy in preterm-born infants require optimizing nutrition; only then, prognosis, growth, neurodevelopment, and overall quality of life can improve. In this article, we discuss the various evidence-based feeding and nutritional strategies that can be applicable even in resource-limited settings, where resources and infrastructure for advanced neonatal care are limited. This article addresses nutrition, feeding strategies, and growth monitoring in the neonatal intensive care unit and at discharge to optimize nutrition, growth, and development.

Impact of Nutrient Intake on Body Composition in Very Low-Birth Weight Infants Following Early Progressive Enteral Feeding

Preterm infants have increased body adiposity at term-equivalent age and risk of adverse metabolic outcomes. The aim of the study was to define how nutrient intake may impact body composition (BC) of very low-birth weight infants fed with early progressive enteral feeding and standard fortification. Eighty-six infants with <1500 g birth weight were included in the BC study and stratified into extremely preterm (EP) and very preterm (VP) groups. Nutrient intake was calculated during the first 28 days and BC assessed by dual X-ray absorptiometry at discharge and by skinfold thickness at 12 months of corrected age (CA). Total nutrient intake did not differ between the groups. EP infants had a higher fat mass percentage at discharge than VP infants (24.8% vs. 19.4%, p < 0.001); lean mass did not differ. None of the nutrients had any impact on BC of EP infants. Protein intake did not result in a higher lean mass in either group; fat intake was a significant predictor of increased fat mass percentage in VP infants at discharge (p = 0.007) and body adiposity at 12 months of CA (p = 0.021). Nutritional needs may depend on gestational age and routine fortification should be used with caution in more mature infants.

Infant body composition: A comprehensive overview of assessment techniques, nutrition factors, and health outcomes

Body composition assessment is a valuable tool for clinical assessment and research that has implications for long-term health. Unlike traditional measurements such as anthropometrics or body mass index, body composition assessments provide more accurate measures of body fatness and lean mass. Moreover, depending on the technique, they can offer insight into regional body composition, bone mineral density, and brown adipose tissue. Various methods of body composition assessment exist, including air displacement plethysmography, dual-energy x-ray absorptiometry, bioelectrical impedance, magnetic resonance imaging, D3 creatine, ultrasound, and skinfold thickness, each with its own strengths and limitations. In infants, several feeding practices and nutrition factors are associated with body composition outcomes, such as breast milk vs formula feeding, protein intake, breast milk composition, and postdischarge formulas for preterm infants. Longitudinal studies suggest that body composition in infancy predicts later body composition, obesity, and other cardiometabolic outcomes in childhood, making it a useful early marker of cardiometabolic health in both term and preterm infants. Emerging evidence also suggests that body composition during infancy predicts neurodevelopmental outcomes, particularly in preterm infants at high risk of neurodevelopmental impairment. The purpose of this narrative review is to provide clinicians and researchers with a comprehensive overview of body composition assessment techniques, summarize the links between specific nutrition practices and body composition in infancy, and describe the neurodevelopmental and cardiometabolic outcomes associated with body composition patterns in term and preterm infants.

Trends in Preterm Body Composition and Neurodevelopmental Outcomes after Discharge

INTRODUCTION

Body composition, specifically fat-free mass (FFM), of preterm infants is associated with improved neurodevelopmental outcomes. Little is known about body composition of preterm infants after discharge. Preterm body composition was measured by air displacement plethysmography (ADP) at two time points, inpatient (35-40 weeks postmenstrual age [PMA]) and outpatient (48-58 weeks PMA), with neonatal factors and neurodevelopmental testing at 4-6 months corrected age. We hypothesized increased FFM is positively associated with neurodevelopment.

METHODS

From 2007 to 2011, 510 infants admitted to the Medical University of South Carolina's neonatal intensive care unit underwent ADP. A total of 379 of 510 (74%) had anthropometrics at birth, an ADP scan with FFM, fat mass, fat percent z-scores, and an outpatient neurodevelopmental evaluation (CAT/CLAMS, Peabody Gross Motor). Variables were compared using multivariate analyses for body composition measurements.

RESULTS

The infants were 32 ± 4.8 weeks gestational age at birth with an average birth weight of 1,697 ± 932 g. Most (56%) infants received maternal milk at discharge. CAT, CLAMS, and gross motor scores had positive correlations with FFM z-scores at inpatient and outpatient ADP (p < 0.05). Receiving maternal milk at discharge was positively associated with cognitive (β = 0.22, p < 0.05) and language scores (β = 0.26, p < 0.05).

CONCLUSION

Increased FFM is associated with improved cognitive, language, and gross motor testing. Maternal milk was positively associated with language and cognitive scores.

Human Milk Fortification for Very Preterm Infants: Toward Optimal Nutrient Delivery, Neonatal Intensive Care Unit Growth, and Long-Term Outcomes

Human milk is the preferred diet for very preterm infants due to short-term and long-term benefits for health and neurodevelopment. Fortification of human milk is required to deliver sufficient nutrients to attain recommended growth targets during the neonatal hospitalization. Intrinsic variability in human milk composition poses a challenge in clinical practice because some infants fail to meet recommended nutrient intakes even with existing approaches of standard (fixed-dose) and adjustable fortification. Individually targeted fortification is an emerging strategy to minimize nutrition delivery gaps through application of point-of-care human milk analysis and has potential to improve growth and related outcomes.

Differential associations between body composition indices and neurodevelopment during early life in term-born infants: findings from the Pakistan cohort: Multi-Center Body Composition Reference Study

OBJECTIVE

We examined associations between fat free mass (FFM) and fat mass (FM) accretion during the first 1000 days of life and neurodevelopment in term-born, low-risk infants from Karachi, Pakistan.

DESIGN

Prospective, observational study nested within the larger Multi-Center Body Composition Reference Study. FFM, FM, and fat% were estimated using measured deuterium dilution method. Neurodevelopmental outcomes were assessed at 24 months on the INTER-NDA (INTERGROWTH-21st Project Neurodevelopment Assessment) (n = 132).

RESULTS

Children with gross motor delays had significantly lower FFM at 18 months (8.01 ± 0.97 kg vs. 7.55 ± 0.20 kg). Children with positive and negative behavior problems had significantly higher fat% at 24 months (20.62 ± 4.30% vs. 18.23 ± 5.46%) and 20.89 ± 4.24% vs. 18.54 ± 5.38%). No associations remained significant after adjusting for covariates. Trajectory modeling showed that between 12 and 18 months, negative behavior scores changed by 13.8 points for every standard deviation change in fat accretion.

CONCLUSIONS

Our findings highlight the importance of balancing neurodevelopment and metabolic risk when designing nutritional interventions for young children.

Early-Life Slow Enteral Feeding Progression Pattern Is Associated with Longitudinal Head-Size Growth Faltering and Neurodevelopmental Impairment Outcomes in Extremely Preterm Infants

OBJECTIVE

To determine whether feeding progression patterns in the first eight postnatal weeks, depicted by clustering analysis of daily enteral feeding volume, are associated with longitudinal head-circumference (HC) growth and neurodevelopmental outcomes in extremely preterm (EP) infants.

METHODS

200 infants who were admitted at gestational ages 23-27 weeks between 2011 and 2018; survived to discharge; and underwent longitudinal HC growth measurements at birth, term-equivalent age (TEA), corrected age (CA) 6-month, 12-month, and 24-month; and neurodevelopmental assessment using the Bayley Scales of Infant Development at CA 24 months were included for analysis.

RESULTS

kmlShape analysis identified two distinct enteral feeding progression patterns: fast progression in 131 (66%) infants and slow progression in 69 (34%) infants. Compared to the fast progression group, the slow progression group showed significantly lower daily enteral volumes after day 13, was older in postnatal age reaching full feeding, had a higher rate of Delta z scores of HC (zHC) < -1 (p < 0.001) between birth and TEA, and displayed lower longitudinal zHC from TEA to CA 24 months. The slow progression group also showed higher rates of microcephaly [42% vs. 16%, p < 0.001; adjusted odd ratio (aOR): 3.269, p = 0.001] and neurodevelopmental impairment (NDI) (38% vs. 19%, p = 0.007; aOR: 2.095, p = 0.035) at CA 24 months. For NDI, the model including feeding progression patterns showed a lower Akaike information criterion score and a better goodness of fit than the model that did not include feeding patterns.

CONCLUSION

Characterizing feeding progression pattern may help identify EP infants at high-risk of head-size growth faltering and NDI at early childhood.

Growth During Infancy After Extremely Preterm Birth: Associations with Later Neurodevelopmental and Health Outcomes

OBJECTIVE

To evaluate associations between changes in weight, length, and weight/length ratio during infancy and outcomes later in life among individuals born extremely preterm.

STUDY DESIGN

Among participants in the Extremely Low Gestational Age Newborn (ELGAN) study, we measured weight and length at discharge from the neonatal intensive care unit (NICU) and at age 2 years and evaluated neurocognitive, psychiatric, and health outcomes at age 10 years and 15 years. Using multivariable logistic regression, we estimated associations between gains in weight, length, and weight/length ratio z-scores between discharge and 2 years and outcomes at 10 and 15 years. High gain was defined as the top quintile of change; low gain, as the bottom quintile of change.

RESULTS

High gains in weight and weight/length were associated with greater odds of obesity at 10 years, but not at 15 years. These associations were found only for females. High gain in length z-score was associated with lower odds of obesity at 15 years. The only association found between high gains in growth measures and more favorable neurocognitive or psychiatric outcomes was between high gain in weight/length and lower odds of cognitive impairment at age 10 years.

CONCLUSIONS

During the 2 years after NICU discharge, females born extremely preterm with high gains in weight/length or weight have greater odds of obesity at 10 years, but not at 15 years. Infants with high growth gains in the 2 years after NICU discharge have neurocognitive and psychiatric outcomes in middle childhood and adolescence similar to those of infants with lower gains in weight and weight/length.

Associations of body composition with regional brain volumes and white matter microstructure in very preterm infants

OBJECTIVE

To determine associations between body composition and concurrent measures of brain development including (1) Tissue-specific brain volumes and (2) White matter microstructure, among very preterm infants at term equivalent age.

DESIGN

Prospective observational study.

SETTING

Single-centre academic level III neonatal intensive care unit.

PATIENTS

We studied 85 infants born <33 weeks' gestation.

METHODS

At term equivalent age, infants underwent air displacement plethysmography to determine body composition, and brain MRI from which we quantified tissue-specific brain volumes and fractional anisotropy (FA) of white matter tracts. We estimated associations of fat and lean mass Z-scores with each brain outcome, using linear mixed models adjusted for intrafamilial correlation among twins and potential confounding variables.

RESULTS

Median gestational age was 29 weeks (range 23.4-32.9). One unit greater lean mass Z-score was associated with larger total brain volume (10.5 cc, 95% CI 3.8 to 17.2); larger volumes of the cerebellum (1.2 cc, 95% CI 0.5 to 1.9) and white matter (4.5 cc, 95% CI 0.7 to 8.3); and greater FA in the left cingulum (0.3%, 95% CI 0.1% to 0.6%), right uncinate fasciculus (0.2%, 95% CI 0.0% to 0.5%), and right posterior limb of the internal capsule (0.3%, 95% CI 0.03% to 0.6%). Fat Z-scores were not associated with any outcome.

CONCLUSIONS

Lean mass-but not fat-at term was associated with larger brain volume and white matter microstructure differences that suggest improved maturation. Lean mass accrual may index brain growth and development.

Randomised controlled trial of human derived breast milk fortifier versus bovine milk fortifier on body composition in very preterm babies

BACKGROUND

Preterm infants receiving a diet of exclusive human milk compared to predominantly preterm formula have lower weight and non-adipose tissue mass by term. Human milk fortification is recommended. However, it is not known if the protein source affects body composition.

AIMS

To compare the effect of an exclusive human milk based diet (intervention) with a diet containing cow milk products (control) on body composition.

PARTICIPANTS

Infants born below 30 weeks gestation.

STUDY DESIGN

Randomised multicentre, open label, controlled trial. Infants preferentially received their own mother's milk. Infants were randomised to either an exclusive human milk diet (human milk formula to make up a shortfall in own mother's milk and human milk derived fortifier) or cow milk-based supplementation (preterm formula to make up a shortfall in own mother's milk and cow milk-based fortifier). Fortification began at an enteral intake of 150 ml/kg/day. Infants underwent whole-body magnetic resonance imaging at term.

PRIMARY OUTCOME

Body composition (adipose tissue (ATM) and non-adipose tissue mass (N-ATM)) at term.

RESULTS

We randomly assigned 38 infants to intervention (n = 19) and control arms (n = 19). Primary outcomes were analysed in 15 infants in the intervention arm and 12 in the control arm. The estimates of the effect of the intervention following adjustment for length and sex, were non-significant (ATM (kg): 0.137, 95 % confidence interval (CI) -0.01, 0.29; N-ATM: -0.137; -0.01, 0.29).

CONCLUSIONS

We identified no clinically relevant differences in body composition in preterm babies <30 weeks gestation receiving a macronutrient-equivalent exclusive human milk diet compared with a diet containing cow milk products.

Effect of parenteral nutrition duration on patterns of growth and body composition in very low-birth-weight premature infants

BACKGROUND

Parenteral nutrition (PN) is essential to support premature infants' growth and varies with enteral nutrition (EN) advancement rates. Data on PN duration's impact on premature infants' growth are limited. The aim of this multicenter observational study was to determine the effect of early PN duration on body composition at term corrected gestational age (CGA) in very low-birth-weight (VLBW) premature infants.

METHODS

VLBW infants exposed to PN in the first week of life and exposed to significantly different EN regimens were divided into two groups on the basis of early PN duration. Infants with a birth weight (BW) <1000 g and PN duration <28 days and infants with a BW 1000-1500 g and PN duration <14 days were assigned to the "short-PN" group. Infants receiving PN for longer durations were assigned to the "long-PN" group. Body composition was assessed via air displacement plethysmography at term CGA or before discharge.

RESULTS

Sixty-two and 53 infants were assigned to the short-PN and long-PN groups, respectively. The two groups were significantly different in BW and GA, so a nested case-control study was conducted after matching 36 infant pairs. Infants in the long-PN group had significantly lower fat-free mass (FFM) z-scores, but both groups had comparable fat mass (FM) z-scores. Long PN was a significant negative predictor of FFM z-score in the multivariate regression analysis.

CONCLUSION

In VLBW premature infants, PN duration is negatively associated with FFM z-scores at term CGA without affecting FM z-scores.