Evaluation of air-displacement plethysmography for body composition assessment in preterm infants

Body composition assessment in 6-month-old infants: A comparison of two- and three-compartment models using data from the Baby-bod study

BACKGROUND/OBJECTIVES

An appreciation of infant body composition is helpful to understand the 'quality' of growth in early life. Air displacement plethysmography (ADP) using PEA POD and the deuterium dilution (DD) technique are commonly used body composition approaches in infants. We evaluated the comparability of body composition assessed using both techniques with two-compartment (2C) and three-compartment (3C) models in 6-month-old infants.

SUBJECTS/METHODS

Infant fat mass (FM) and percent fat mass (%FM) obtained from a 2C model using PEA POD (2C-PP) and a 2C model using the deuterium dilution technique (2C-DD) were compared to those derived from a 3C model, and to each other, using Bland-Altman analysis and Deming regression.

RESULTS

Measurements were available from 68 infants (93% Caucasian, 53% male). The mean biases were not significant between any of the method comparisons. However, significant constant and proportional biases were identified in 2C-DD vs 3C and 2C-PP vs 2C-DD, but not in the 2C-PP vs 3C comparison. Furthermore, we observed significant associations between the mean differences and infants' percent total body water (%TBW).

CONCLUSIONS

While no significant between-method mean differences were found in body composition estimates, some comparisons revealed significant constant and proportional biases and notable associations between the mean differences and %TBW were observed. Our results emphasise the importance of method choice, ensuring methodological uniformity in long-term studies, and carefully considering and regulating multiple pre-analytical variables, such as the hydration status of the participants.

Body Composition Analysis of the Clinical Routine Using Air Displacement Plethysmography: Age-Group-Specific Feasibility Analysis among Preterm Infants

Body composition assessments using air displacement plethysmography (ADP, PEAPOD®) have been introduced into clinical practice at a few neonatal units. To allow accurate body composition assessments in term and preterm infants, a workflow for routine testing is needed. The aim of this study was to analyze the feasibility of weekly routine ADP testing. We analyzed (1) postnatal ages at first ADP assessment, (2) the number of weekly routine in-hospital assessments, and (3) the workload of body composition measurements using ADP in clinical practice on the basis of an retrospective analysis of our own clinical operating procedures. The retrospective analysis of weekly routine ADP testing proved feasible at Nuremberg Children's Hospital. The analysis of postnatal age at the first ADP test revealed differences across groups, with extremely preterm infants starting at a mean postmenstrual age of 36.6 weeks, very preterm infants starting at 34.2 weeks, and moderate to late preterm infants starting at 35.3 weeks. The mean number of tests before discharge was significantly greater in the extremely preterm group (n = 3.0) than in the very preterm (n = 2.4) and moderate to late preterm groups (n = 1.7). The workload of the procedure is reasonable, at 8-13 min per test cycle. The study proved that weekly routine ADP assessments in preterm infants are feasible. However, the initiation of routine testing in extremely preterm infants starts at a significantly greater postnatal age than in the more mature population. ADP assessments can be safely and easily integrated into clinical practice and may be valuable tools for providing additional information on nutritional status and infant growth. A standardized routine protocol allowing identical measurement conditions across healthcare institutions and a standardized interpretation tool for age-adapted body composition data, however, would improve comparability and usability.

Association between preterm infant body composition in the first 3 months of life and preschool age: a cohort study

Compared with full-term infants, preterm infants have fat-free mass deficit in the first months of life, which increases the risk of metabolic diseases in the future. In this cohort of children born under 32-week gestational age or less than 1500 g, we aimed to evaluate the associations of body composition at term equivalent age and in the first 3 months of life with fat-free mass and fat mass percentage at 4 to 7 years of life. Body composition assessments by air displacement plethysmography and anthropometry were performed at term, at 3 months of corrected age, and at 4 to 7 years of age. Multiple linear regression analysis was used to observe the associations between body composition at these ages. At term, fat mass percentage showed a negative association and fat-free mass a positive association with fat-free mass at 4 to 7 years. The fat-free mass at 3 months and the gain in fat-free mass between term and 3 months showed positive associations with fat-free mass at 4 to 7 years.   Conclusion: Body composition at preschool age is associated with fat-free mass in the first 3 months of life, a sensitive period for the risk of metabolic diseases. What is Known: • Preterm infants have a deficit in fat-free mass and high adiposity at term equivalent age compared to full-term infants. • Fat-free mass reflects metabolic capacity throughout life and therefore is considered a protective factor against the risk of metabolic syndrome. What is New: •Fat-free mass gain in the first 3 months of corrected age is associated with fat-free mass at preschool and school ages. •The first 3 months of life is a sensitive period to the risk of metabolic diseases.

Reproducibility of Air Displacement Plethysmography in Term and Preterm Infants-A Study to Enhance Body Composition Analysis in Clinical Routine

The quality-initiative analysis of weekly duplicate PEAPOD® body composition measurements was conducted from clinical practice (January to September 2021) on preterm and term infants without respiratory support. Statistical analysis, including regression analysis, Bland-Altman plots and cv-root-mean-square tests, was performed. A total of 188 duplicate (376 individual) measurements were collected from 119 infants (88 preterm, 31 term). The median absolute difference between duplicates was 31.5 g for fat-free mass (FFM). Linear correlation analysis showed R2 = 0.97 for FFM. The absolute differences in FFM and fat mass did not significantly correlate with increasing age. The %FFM differed (p = 0.02) across body weight groups of 1 kg < BW ≤ 2 kg (1.8%; IQR: 0.8, 3.6) and BW > 3 kg (0.9%; IQR: 0.3, 2.1). The median absolute differences were 1 g (IQR: 0.4, 3.1) for body weight and 5.6 mL (IQR: 2.1, 11.8) for body volume. Body volume estimation is charged with a constant absolute error, which is the main factor for differences between repeated body composition assessments. This error becomes more prominent in infants with lower body weights. Nevertheless, reproducibility of weekly PEAPOD testing is sufficient to monitor body compartment changes, offering a foundation for nutritional decisions in both preterm and term infants.

Infant Body Composition in an Asian Pacific Islander Population

BACKGROUND

Normative infant body composition data using air displacement plethysmography (ADP) are from primarily Caucasian populations. Racial differences may exist.

OBJECTIVES

To describe body composition in Asian and Pacific Islander infants and compare them to previously published data on Caucasian infants.

DESIGN

Body composition was measured using ADP with the PEA POD® Infant Body Composition System in 249 healthy full-term newborns in a predominately Asian and Pacific Islander population in Hawaii within the first 3 days of life and compared to published data on Caucasian infants with multiple t-tests adjusted for false discovery rate.

RESULTS

There were no differences in percent body fat between Asian, Pacific Islander, or mixed race Asian Pacific Islander infants. Both Asian and Pacific Islander infants had significantly higher percent body fat than Caucasians from Italy in Europe (13.2% and 11.8% vs 8.9%, p < 0.01 among males, 15.3% and 15.6% vs 8.7%, p < 0.01 among females) but not when compared to Caucasians from New York.

CONCLUSIONS

Racial and geographical differences in body composition exist at birth between Asian and Pacific Islanders and other Caucasian cohorts. Previously published ADP nomograms must be interpreted with caution. Future studies are needed to investigate the impact of environmental, perinatal, and genetic factors on infant body composition and its relationship to future cardiometabolic morbidity. Efforts to address racial disparities in cardiometabolic disease measures must also address pre-conceptual maternal health, which may have long-term implications on future body composition in offspring.

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.

Development and validation of anthropometric-based fat-mass prediction equations using air displacement plethysmography in Mexican infants

BACKGROUND/OBJECTIVES

Fat-mass (FM) assessment since birth using valid methodologies is crucial since excessive adiposity represents a risk factor for adverse metabolic outcomes.

AIM

To develop infant FM prediction equations using anthropometry and validate them against air-displacement plethysmography (ADP).

SUBJECTS/METHODS

Clinical, anthropometric (weight, length, body-mass index -BMI-, circumferences, and skinfolds), and FM (ADP) data were collected from healthy-term infants at 1 (n = 133), 3 (n = 105), and 6 (n = 101) months enrolled in the OBESO perinatal cohort (Mexico City). FM prediction models were developed in 3 steps: 1) Variable Selection (LASSO regression), 2) Model behavior evaluation (12-fold cross-validation, using Theil-Sen regressions), and 3) Final model evaluation (Bland-Altman plots, Deming regression).

RESULTS

Relevant variables in the FM prediction models included BMI, circumferences (waist, thigh, and calf), and skinfolds (waist, triceps, subscapular, thigh, and calf). The R2 of each model was 1 M: 0.54, 3 M: 0.69, 6 M: 0.63. Predicted FM showed high correlation values (r ≥ 0.73, p < 0.001) with FM measured with ADP. There were no significant differences between predicted vs measured FM (1 M: 0.62 vs 0.6; 3 M: 1.2 vs 1.35; 6 M: 1.65 vs 1.76 kg; p > 0.05). Bias were: 1 M -0.021 (95%CI: -0.050 to 0.008), 3 M: 0.014 (95%CI: 0.090-0.195), 6 M: 0.108 (95%CI: 0.046-0.169).

CONCLUSION

Anthropometry-based prediction equations are inexpensive and represent a more accessible method to estimate body composition. The proposed equations are useful for evaluating FM in Mexican infants.

A pilot study to disentangle the infant gut microbiota composition and identification of bacteria correlates with high fat mass

Background: At birth, the human intestine is colonized by a complex community of microorganisms known as gut microbiota. These complex microbial communities that inhabit the gut microbiota are thought to play a key role in maintaining host physiological homeostasis. For this reason, correct colonization of the gastrointestinal tract in the early stages of life could be fundamental for human health. Furthermore, alterations of the infant microbiota are correlated with the development of human inflammatory diseases and disorders. In this context, the possible relationships between intestinal microbiota and body composition during infancy are of great interest. Methods: In this study, we have performed a pilot study based on 16S rRNA gene profiling and metagenomic approaches on repeatedly measured data on time involving a cohort of 41 Italian newborns, which is aimed to investigate the possible correlation between body fat mass percentage (FM%) and the infant gut microbiota composition. Results and conclusion: The taxonomical analysis of the stool microbiota of each infant included in the cohort allowed the identification of a specific correlation between intestinal bacteria, such as Bifidobacterium and Veillonella, and the increase in FM%. Moreover, the analysis of the infant microbiome's metabolic capabilities suggested that the intestinal microbiome functionally impacts the human host and its possible influence on host physiology.

Body composition in preterm infants: a systematic review on measurement methods

BACKGROUND

There are several methods to measure body composition in preterm infants. Yet, there is no agreement on which method should be preferred.

METHODS

PubMed, Embase.com, Wiley/Cochrane Library, and Google Scholar were searched for studies that reported on the predictive value or validity of body composition measurements in preterms, up to 6 months corrected age.

RESULTS

Nineteen out of 1884 identified studies were included. Predictive equations based on weight and length indices, body area circumferences, skinfold thickness, bioelectrical impedance, and ultrasound did not show agreement with body composition measured with air displacement plethysmography (ADP), dual-energy x-ray absorptiometry (DXA), magnetic resonance imaging (MRI), or isotope dilution. ADP agreed well with fat mass density measured by isotope dilution (bias -0.002 g/ml, limits of agreement ±0.012 g/ml, n = 14). Fat mass percentage measured with ADP did not agree well with fat mass percentage measured by isotope dilution (limits of agreement up to ±5.8%) and the bias between measurements was up to 2.2%. DXA, MRI, and isotope dilution were not compared to another reference method in preterms.

CONCLUSIONS

DXA, ADP, and isotope dilution methods are considered trustworthy validated techniques. Nevertheless, this review showed that these methods may not yield comparable results.

IMPACT

Based on validation studies that were conducted in a limited number of study subjects, weight and length indices, body area circumferences, skinfold thickness, bioelectrical impedance, and ultrasound seem to be a poor representation of body composition in preterm infants. DXA, ADP, and isotope dilution methods are considered trustworthy and validated techniques. Nevertheless, these methods may not yield comparable results.

Predictive models of newborn body composition: a systematic review

OBJECTIVE

To analyze the prediction models of fat-free mass and fat mass of neonates who had air displacement plethysmography as a reference test.

DATA SOURCE

A systematic review of studies identified in the PubMed, Virtual Health Library (BVS), SciELO, and ScienceDirect databases was carried out. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist was used for inclusion of studies, the Transparent Reporting of a Multivariable Prediction Model for Individual Prognosis or Diagnosis (TRIPOD) report was used to select only predictive models studies, and the Prediction Model Risk of Bias Assessment Tool (PROBAST) was used to assess the risk of bias in the models.

DATA SYNTHESIS

This study is registered in PROSPERO with identification CRD42020175048. Five hundred and three studies were found during the searches, and only four papers (six models) were eligible. Most studies (three) used the sum of different skinfolds to predict neonatal body fat and all presented weight as the variable with the highest contribution to predicting neonatal body composition. Two models that used skinfolds showed high coefficients of determination and explained, significantly, 81% of the body fat measured by air displacement plethysmography, while the models using bioimpedance did not find a significant correlation between the impedance index and the fat-free mass.

CONCLUSIONS

The few studies found on this topic had numerous methodological differences. However, the subscapular skinfold was a strong predictor of neonatal body fat in three studies. It is noteworthy that such model validation studies should be carried out in the future, allowing them to be subsequently applied to the population. The development of these models with low-cost tools will contribute to better nutritional monitoring of children and could prevent complications in adulthood.

Body composition measurement for the preterm neonate: using a clinical utility framework to translate research tools into clinical care

Body composition analysis to distinguish between fat mass and fat-free mass is an established research approach to assess nutritional status. Within neonatal medicine, preterm infant body composition is linked with later health outcomes including neurodevelopment and cardiometabolic health. Mounting evidence establishing fat-free mass as an indicator of nutritional status, coupled with the availability of testing approaches that are feasible to use in preterm infants, have enhanced interest in measuring body composition in the neonatal intensive care unit (NICU) setting. In this paper, we use the concept of clinical utility-the added value of a new methodology over current standard care-as a framework for assessing several existing body composition methodologies with potential for clinical application to preterm neonates. We also use this framework to identify remaining knowledge gaps and prioritize efforts to advance our understanding of clinically-oriented body composition testing in the NICU.

Body composition at 4 to 7 years of age in children born <32 weeks gestational age or 1500 g: A cohort study

BACKGROUND

Small for gestational age preterm infants show differences in body composition when compared to those appropriate for gestational age at term, which have consequences on metabolism.

AIM

To compare growth and body composition of children born small and appropriate for gestational age between 4 and 7 years.

METHOD

A Cohort of small and appropriate for gestational age infants <32 weeks or 1500 g were followed at term and 3 months corrected ages and at 4 to 7 years. Body composition assessment by air displacement plethysmography and anthropometry were performed at all moments. Differences between the two groups were assessed using t-student and Chi-square tests.

RESULTS

Ninety-four infants were included at term (26 small and 68 appropriate for gestational age); 88 at 3 months (24 small and 64 appropriate for gestational age) and 47 between 4 and 7 years (11 small and 36 appropriate for gestational age). At term, small for gestational age infants had lower fat-free mass, fat mass, weight and length compared with those appropriate for gestational age (p < 0.001). At 3 months, fat-free mass (grams) remained lower in small for gestational age group (p < 0.001). Between 4 and 7 years, body composition and anthropometry were similar between the groups.

CONCLUSION

Between 4 and 7 years, children born small and appropriate for gestational age had similar body composition. New long-term longitudinal studies are necessary to understand the influence of fat-free mass and fat mass in the first months of age on body composition throughout life.

Preterm birth and metabolic implications on later life: A narrative review focused on body composition

Preterm newborn infants are characterized by low body weight and lower fat mass at birth compared with full-term newborn neonates. Conversely, at term corrected age, body fat mass is more represented in preterm newborn infants, causing a predisposition to developing metabolic syndrome and cardiovascular diseases in later life with a different risk profile in men as compared with women. Postnatal growth is a complex change in anthropometric parameters and body composition. Both quantity and quality of growth are regulated by several factors such as fetal programming, early nutrition, and gut microbiota. Weight gain alone is not an optimal indicator of nutritional status as it does not accurately describe weight quality. The analysis of body composition represents a potentially useful tool to predict later metabolic and cardiovascular risk as it detects the quality of growth by differentiating between fat and lean mass. Longitudinal follow-up of preterm newborn infants could take advantage of body composition analysis in order to identify high-risk patients who apply early preventive strategies. This narrative review aimed to examine the state-of-the-art body composition among born preterm children, with a focus on those in the pre-school age group.

Energy expenditure and body composition in infants with bronchopulmonary dysplasia at term age

In this cross-sectional study, conducted in a cohort of infants with a gestational age of < 32 weeks, we aimed to evaluate and compare resting energy expenditure (REE) and body composition between infants who developed bronchopulmonary dysplasia (BPD) and those who did not. REE and body composition were assessed at term equivalent age using indirect calorimetry and air displacement plethysmography. Anthropometric measurements (weight, head circumference, and length) were obtained and transformed into Z-scores per the Fenton (2013) growth curve, at birth and at term equivalent age. Forty-two infants were included in this study, of which 26.2% developed BPD. Infants with BPD had significantly higher energy expenditure at term equivalent age, with no difference in body composition between the two groups.

CONCLUSION

Despite expending more energy, infants with BPD maintained a similar body composition distribution to those without BPD, and this is likely due to the recommended nutritional approach.

WHAT IS KNOWN

• Greater resting energy expenditure impairs growth of preterm infants with bronchopulmonary dysplasia.

WHAT IS NEW

• Although preterm infants with bronchopulmonary dysplasia had a higher resting energy expenditure at the corrected term age, this did not affect their body composition and growth.

Energy Expenditure, Protein Oxidation and Body Composition in a Cohort of Very Low Birth Weight Infants

The nutritional management of preterm infants is a critical point of care, especially because of the increased risk of developing extrauterine growth restriction (EUGR), which is associated with worsened health outcomes. Energy requirements in preterm infants are simply estimated, so the measurement of resting energy expenditure (REE) should be a key point in the nutritional evaluation of preterm infants. Although predictive formulae are available, it is well known that they are imprecise. The aim of our study was the evaluation of REE and protein oxidation (Ox) in very low birth weight infants (VLBWI) and the association with the mode of feeding and with body composition at term corrected age. Methods: Indirect calorimetry and body composition were performed at term corrected age in stable very low birth weight infants. Urinary nitrogen was measured in spot urine samples to calculate Ox. Infants were categorized as prevalent human milk (HMF) or prevalent formula diet (PFF). Results: Fifty VLBWI (HMF: 23, PFF: 27) were evaluated at 36.48 ± 0.85 post-conceptional weeks. No significant differences were found in basic characteristics or nutritional intake in the groups at birth and at the assessment. No differences were found in the REE of HMF vs. PFF (59.69 ± 9.8 kcal/kg/day vs. 59.27 ± 13.15 kcal/kg/day, respectively). We found statistical differences in the protein-Ox of HMF vs. PFF (1.7 ± 0.92 g/kg/day vs. 2.8 ± 1.65 g/kg/day, respectively, p < 0.01), and HMF infants had a higher fat-free mass (kg) than PFF infants (2.05 ± 0.26 kg vs. 1.82 ± 0.35 kg, respectively, p < 0.01), measured with air displacement plethysmography. Conclusion: REE is similar in infants with a prevalent human milk diet and in infants fed with formula. The HMF infants showed a lower oxidation rate of proteins for energy purposes and a better quality of growth. A greater amount of protein in HMF is probably used for anabolism and fat-free mass deposition. Further studies are needed to confirm our hypothesis.

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.

Ultrasound measurements of abdominal muscle thickness are associated with postmenstrual age at full oral feedings in preterm infants: A preliminary study

BACKGROUND

A premature infant's discharge from the neonatal intensive care unit (NICU) is dependent on factors such as respiratory stability, adequate growth, and the ability to consume oral feeds. Once infants have achieved respiratory stability, a tool that can better predict age at discharge is desirable. Thus, we conducted a secondary data analysis to assess the association between ultrasound measurements of abdominal muscle thickness and postmenstrual age (PMA) at full oral feedings.

METHODS

Forty-nine (n = 49) healthy, premature infants (mean gestational age = 32 weeks) were recruited from the NICU. Anthropometric measurements and ultrasound measurements of the rectus abdominis were conducted when infants were medically stable. Fat-free mass (FFM) was obtained using air displacement plethysmography. The relationship between ultrasound measurements of muscle thickness and PMA at full oral feedings was assessed using linear regression analysis. The relationship between FFM z-scores and PMA at full oral feedings was also assessed for comparison.

RESULTS

When adjusting for gestational age at birth, PMA at measurement, days of positive pressure respiratory support, weight, and length, ultrasound measurements of abdominal muscle thickness were independently, negatively associated with PMA at full oral feedings (β estimate: -0.71, P = .03).

CONCLUSION

Preliminary results suggest infants with greater abdominal muscle thickness may reach full oral feedings at an earlier PMA (nearly 1 week per millimeter). Thus, ultrasound measurements of abdominal muscle thickness may be helpful in assessing readiness for discharge in healthy preterm infants. Further research is needed for development and validation of a prediction equation.

Weight for length measures may not accurately reflect adiposity in preterm infants born appropriate for gestational age during hospitalisation or after discharge from the neonatal intensive care unit

BACKGROUND

Weight/length (W/L) indices are poor surrogates for adiposity in preterm infants born appropriate for gestational age (AGA) at birth, but whether the association subsequently improves is unknown.

OBJECTIVE

To determine if W/L indices accurately reflect adiposity in premature infants born AGA in later infancy.

METHODS

Associations between W/L indices and fat mass, fat mass index and percent body fat (%BF) obtained via air displacement plethysmography (ADP) were examined in 260 preterm infants (majority born AGA) at 28 to 63 weeks' postmenstrual age (PMA). Accuracy of W/L indices as indicators of adiposity was assessed by proportion of variance explained (R² ) and root mean square error from linear regression of adiposity on W/L indices and proportion of infants misclassified by W/L indices. Accuracy was further compared in term vs preterm infants at term-equivalent age. The impact of early vs late preterm status on associations between W/L indices and %BF was also examined.

RESULTS

BMI and W/L were most strongly associated with %BF but yielded poorly fitting models (maximum R² = 0.35; 53% misclassification). A significant interaction of W/L indices and early vs late preterm status on %BF revealed that estimation of %BF differs by status. Accuracy of W/L indices was worse in preterm infants at term-equivalent age.

CONCLUSIONS

W/L indices were not good indicators of adiposity in preterm infants from 28 to 63 weeks' PMA (born AGA) with all categories of W/L indices combined. Future research should examine whether results are similar in preterm infants born with disproportionate W/L or who experience disproportionate growth postnatally.

Infant body composition assessment in the neonatal intensive care unit (NICU) using air displacement plethysmography: Strategies for implementation into clinical workflow

Nutritional management is integral to infant care in the neonatal intensive care unit (NICU). Recent research on body composition that specifically evaluated fat and fat-free mass has improved our understanding of infant growth and nutritional requirements. The need for body composition monitoring in infants is increasingly recognized as changes in fat mass and fat-free mass associated with early growth can impact clinical outcomes. With the availability of air displacement plethysmography (ADP) as a noninvasive method for assessing infant body composition and published normative gestational age- and sex-specific body composition curves, it is justifiable to integrate this innovation into routine clinical care. Here we describe our experiences in implementing body composition measurement using ADP in routine clinical care in different NICU settings.

Targeting human milk fortification to improve very preterm infant growth and brain development: study protocol for Nourish, a single-center randomized, controlled clinical trial

Background

Human milk is recommended for very preterm infants, but its variable macronutrient content may contribute to undernutrition during a critical period in development. We hypothesize that individually targeted human milk fortification is more effective in meeting macronutrient requirements than the current standard of care.

Methods

We designed a single-center randomized, controlled trial enrolling 130 infants born < 31 completed weeks’ gestation. Participants will receive fortified maternal and/or pasteurized donor milk but no formula. For participants in the intervention group, milk will be individually fortified with protein and fat modulars to achieve target levels based on daily point-of-care milk analysis with mid-infrared spectroscopy, in addition to standard fortification. The study diet will continue through 36 weeks’ postmenstrual age (PMA). Clinical staff and parents will be masked to study group. Primary outcomes include: 1) body length and lean body mass by air displacement plethysmography at 36 weeks’ PMA; 2) quantitative magnetic resonance imaging-based measures of brain size and microstructure at term equivalent age; and 3) Bayley-IV scales at 2 years’ corrected age.

Discussion

We expect this trial to provide important data regarding the effectiveness of individually targeted human milk fortification in the neonatal intensive care unit (NICU).

Trial registration

NCT03977259, registered 6 June, 2019.

Cardiac and vascular health in late preterm infants

Adults who were born preterm are at increased risk of hypertension and cardiovascular disease in later life. Infants born late preterm are the majority of preterm births; however, the effect of late preterm on risk of cardiovascular disease is unclear. The objective of this study was to assess whether vascular health and cardiac autonomic control differ in a group of late preterm newborn infants compared to a group of term-born infants.A total of 35 healthy late preterm newborn infants, with normal growth (34-36 completed weeks' gestation) and 139 term-born infants (37-42 weeks' gestation) were compared in this study. Aortic wall thickening, assessed as aortic intima-media thickness (IMT) by high-resolution ultrasound, and cardiac autonomic control, assessed by heart rate variability, were measured during the first week of life. Postnatal age of full-term and late preterm infants at the time of the study was 5 days (standard deviation [SD] 5) and 4 days (SD 3), respectively.Infants born late preterm show reduced aortic IMT (574 μm [SD 51] vs. 612 μm [SD 73]) and reduced heart rate variability [log total power 622.3 (606.5) ms2 vs. 1180. 6 (1114.3) ms2], compared to term infants. These associations remained even after adjustment for sex and birth weight.Infants born late preterm show selective differences in markers of cardiovascular risk, with potentially beneficial differences in aortic wall thickness in contrast to potentially detrimental differences in autonomic control, when compared with term-born control infants. These findings provide pathophysiologic evidence to support an increased risk of hypertension and sudden cardiac death in individuals born late preterm.

Macronutrient Intake from Human Milk, Infant Growth, and Body Composition at Term Equivalent Age: A Longitudinal Study of Hospitalized Very Preterm Infants

The variable macronutrient content of human milk may contribute to growth deficits among preterm infants in the neonatal intensive care unit (NICU). In a longitudinal study of 37 infants < 32 weeks gestation, we aimed to (1) determine the between-infant variation in macronutrient intake from human milk and (2) examine associations of macronutrient intake with growth outcomes. We analyzed 1626 human milk samples (median, 43 samples/infant) with mid infrared spectroscopy. Outcomes at term equivalent age were weight, length, head circumference, fat mass, and fat-free mass. Median (range) intakes from human milk were: protein 1.37 (0.88, 2.43) g/kg/day; fat 4.20 (3.19, 5.82) g/kg/day; carbohydrate 8.94 (7.72, 9.85) g/kg/day; and energy 82.5 (68.7, 99.3) kcal/kg/day. In median regression models adjusted for birth size and gestational age, and other covariates, greater intakes of fat and energy were associated with higher weight (0.61 z-scores per g/kg/day fat, 95% CI 0.21, 1.01; 0.69 z-scores per 10 kcal/kg/day, 95% CI 0.28, 1.10), whereas greater protein intake was associated with greater body length (0.84 z-scores per g/kg/day protein, 95% CI 0.09, 1.58). Higher fat intake was also associated with higher fat mass and fat-free mass. Macronutrient intakes from human milk were highly variable and associated with growth outcomes despite routine fortification.

Protein Intakes during Weaning from Parenteral Nutrition Drive Growth Gain and Body Composition in Very Low Birth Weight Preterm Infants

Weaning from parenteral to enteral nutrition is a critical period to maintain an adequate growth in very low birth weight preterm infants (VLBWI). We evaluated the actual daily nutritional intakes during the transition phase (TP) in VLBWI with adequate and inadequate weight growth velocity (GV ≥ 15 vs. GV < 15 g/kg/day). Fat-free mass (FFM) at term-corrected age (TCA) was compared between groups. Based on actual nutritional intakes of infants with adequate growth, we defined a standardized parenteral nutrition bag (SPB) for the TP. One hundred and six VLBWI were categorized as group 1 (G1): [GV < 15 (n = 56)] and group 2 (G2): [GV ≥ 15 (n = 50)]. The TP was divided into two periods: main parenteral nutritional intakes period (parenteral nutritional intakes >50%) (M-PNI) and main enteral nutritional intakes period (enteral nutritional intakes >50%) (M-ENI). Anthropometric measurements were assessed at discharge and TCA, FFM deposition at TCA. During M-PNI, G2 showed higher enteral protein intake compared to G1 (p = 0.05). During M-ENI, G2 showed higher parenteral protein (p = 0.01) and energy intakes (p < 0.001). A gradual reduction in SPB volume, together with progressive increase in enteral volume, allowed nutritional intakes similar to those of G2. At TCA, G2 had higher FFM compared to G1 (p = 0.04). The reasoned use of SPB could guarantee an adequate protein administration, allowing an adequate growth and higher FFM deposition.

Targeted Breast Milk Fortification for Very Low Birth Weight (VLBW) Infants: Nutritional Intake, Growth Outcome and Body Composition

Despite improvements in nutritional management, preterm infants continue to face high rates of postnatal growth restriction. Because variability in breast milk composition may result in protein and energy deficits, targeted fortification has been advocated. We conducted an interventional study to compare body composition and growth outcomes of very low birth weight infants fed targeted protein-fortified human milk (HM) with those fed standard fortified HM. If mother’s own milk was not available, donor milk was used. Weekly analysis of HM with mid-infrared spectroscopy was conducted and additional protein was added to the fortified HM to ensure a protein intake of 4 g/kg/day. Weekly anthropometric measurements were done. Prior to discharge or at 37 weeks, corrected age skinfold thickness (SFT) measurements as well as body composition measurement using air displacement plethysmography were done. Among 36 preterm infants enrolled, those in the targeted group (n = 17) received more protein and had a larger flank SFT at study end than those in the standard group (n = 19). A pilot post-hoc analysis of subjects having at least 30 intervention days showed a 3% higher fat-free mass in the targeted group. Use of a targeted fortification strategy resulted in a higher protein intake and fat-free mass among those receiving longer intervention.

Fat and Fat-Free Mass of Preterm and Term Infants from Birth to Six Months: A Review of Current Evidence

To optimize infant nutrition, the nature of weight gain must be analyzed. This study aims to review publications and develop growth charts for fat and fat-free mass for preterm and term infants. Body composition data measured by air displacement plethysmography (ADP) and dual energy X-ray absorptiometry (DXA) in preterm and term infants until six months corrected age were abstracted from publications (31 December 1990 to 30 April 2019). Age-specific percentiles were calculated. ADP measurements were used in 110 studies (2855 preterm and 22,410 term infants), and DXA was used in 28 studies (1147 preterm and 3542 term infants). At term age, preterm infants had higher percent-fat than term-born infants (16% vs. 11%, p < 0.001). At 52 weeks postmenstrual age (PMA), both reached similar percent-fat (24% vs. 25%). In contrast, at term age, preterm infants had less fat-free mass (2500 g vs. 2900 g) by 400 g. This difference decreased to 250 g by 52 weeks, and to 100 g at 60 weeks PMA (5000 g vs. 5100 g). DXA fat-free mass data were comparable with ADP. However, median percent-fat was up to 5% higher with DXA measurements compared with ADP with PMA > 50 weeks. There are methodological differences between ADP and DXA measures for infants with higher fat mass. The cause of higher fat mass in preterm infants at term age needs further investigation.

Nutrition, Illness and Body Composition in Very Low Birth Weight Preterm Infants: Implications for Nutritional Management and Neurocognitive Outcomes

Preterm infants have altered body composition compared to term infants, which impacts both neurodevelopment and metabolic health, but whether increased dietary intake during hospitalization, independent of illness, may improve body composition is unknown. This prospective, longitudinal study (n = 103) measured fat-free mass (FFM) and percent body fat (%BF) at discharge and four months corrected age for prematurity (CA) in very low birth weight (VLBW) preterm infants. Markers of illness and macronutrient intakes (protein and caloric) were recorded. Bayley Scales of Infant Development-III (BSID) were administered at 12 and 24 months of age in a subset of these infants (n = 66 and n = 50 respectively). Body composition z-scores were calculated using recently developed reference curves. Linear regression was used to test the associations between clinical factors and body composition z-scores, as well as z-scores and BSID scores. Increased calories and protein received in the first week after birth and protein intake throughout hospitalization were associated with increased FFM z-scores at discharge, but not with %BF z-scores. After adjustment for both early acute and chronic illness, associations of nutrient intake with FFM z-score remained unchanged. FFM z-scores at discharge were positively associated with scores on the BSID at 12 and 24 months CA. In conclusion, increased energy and protein intakes both early in hospitalization and across its entire duration are associated with higher FFM at discharge, a key marker for organ growth and neurodevelopment in the VLBW neonate. Optimizing caloric intake, irrespective of illness is critical for enhancing body composition, and by extension, neurodevelopmental outcomes for preterm infants.

Extremely Preterm Infants Have a Higher Fat Mass Percentage in Comparison to Very Preterm Infants at Term-Equivalent Age

Background: Early nutritional support of preterm infants is important because it influences long-term health and development. Body composition has an influence on cardiovascular disease, metabolic syndrome, and neurocognitive outcome in the long term. Objective: To assess body composition in preterm infants <32 weeks of gestation at term-equivalent age and to analyze the influence of an optimized nutritional approach. Methods: This is a prespecified secondary outcome analysis of a prospective observational study comparing the body composition in regard to gestational age. The preterm infants were classified according to gestational age as extremely preterm infants (<28 weeks gestation at birth) and very preterm infants (≥28 weeks gestation at birth) and according to weight percentile as appropriate for gestational age and small for gestational age. Body composition was determined by air displacement plethysmography using the PEA POD. The preterm infants obtained nutrition according to the ESPGHAN 2010 Guidelines. Results: Seventy-four preterm infants were analyzed. The mean (SD) gestational age was 28.7 (2.4) weeks, and birth weight was 1,162 (372) g. Fat mass percentage was significantly higher in extremely preterm infants in comparison to very preterm infants [17.0, 95% confidence interval (CI) 15.9-18.1 vs. 15.5, 95% CI 14.7-16.2]. There was no significant difference of fat mass percentage according to weight percentiles. Conclusions: Extremely preterm infants had a significantly higher fat mass percentage compared to very preterm infants at term-equivalent age. There was no significant difference of fat mass percentage according to weight percentiles.

Enhanced Protein Diet for Preterm Infants: A Prospective, Randomized, Double-blind, Controlled Trial

OBJECTIVE

To evaluate dietary protein's effect on fat accretion and weight gain in hospitalized preterm infants.

METHODS

Prospective, randomized, double-blind, controlled trial of 36 infants born at <32 weeks, hospitalized in a tertiary neonatal intensive care unit. After achieving full enteral volume, infants were randomized to either an enhanced protein diet (EPD) (protein-energy ratio [PER] 4 g/100 calories) or a standard protein diet (SPD) (PER 3 g/100 calories). Macronutrients were calculated using published values for formula, donor milk bank analysis, or weekly analysis of a 24-hour pooled maternal milk sample. Human milk fortifier and/or liquid protein were used to achieve the target PER until discharge or a maximum of 4 weeks. Body composition was measured weekly using air displacement plethysmography. The principal outcomes, rates of weight gain and fat accretion, were compared between groups in linear mixed models.

RESULTS

Thirty-three infants received approximately 17 days of the study diet. Relative weight gain was 21.6 g · kg · day (95% confidence interval [CI] 19.5-23.8) for the EPD group (n = 16) versus 19.1 g · kg · day (95% CI 17.0-21.2) for the SPD group (n = 17), P = 0.095. Baseline percent fat mass (FM) in the EPD group was 5.15% (95% CI 3.58%-6.72%) compared with 7.29% (95% CI 5.73%-8.84%) in the SPD group, P = 0.0517. Percent FM increased 0.398%/day (95% CI 0.308-0.488) for the EPD group versus 0.284%/day (95% CI 0.190-0.379) for the SPD group (P = 0.0878).

CONCLUSIONS

Preterm infants with a lower baseline FM percentage who received an EPD demonstrated a more pronounced catch-up percentage of fat accretion.

Noninvasive assessment of autonomic function in human neonates born at the extremes of fetal growth spectrum

Birth weight is associated with adult cardiovascular disease, such that those at both ends of the spectrum are at increased risk. This may be driven in part by modification to autonomic control, a mechanistic contributor to hypertension. However, birth weight is a relatively crude surrogate of fetal growth; and newborn body composition may more accurately identify the "at risk" infant. Accordingly, we sought to determine whether newborns with high or low body fat have altered autonomic control of vasomotor function and cardiac contractility. Body fat was assessed by air-displacement plethysmography <24 h postnatal. Measures of spontaneous baroreflex sensitivity (sBRS), blood pressure variability (BPV), and dP/dt_max variability were compared between newborns categorized according to established body fat percentiles: high body fat (HBF, >90th percentile, n = 7), low body fat (LBF, ≤10th percentile, n = 12), and normal body fat (control, >25th to ≤75th percentile, n = 23). BPV was similar across body fat percentiles; similarly, low frequency dP/dt_max variability was similar across body fat percentiles. sBRS was reduced in HBF compared to controls (11.0 ± 6.0 vs. 20.1 ± 9.4 msec/mmHg, P = 0.03), but LBF did not differ (18.4 ± 6.0 msec/mmHg, P = 0.80). Across the entire body fat spectrum (n = 62), there was a nonlinear association between newborn body fat and sBRS (P = 0.03) that was independent of birth weight (P = 0.04). Autonomic modulation of vasomotor function and cardiac contractility in the newborn did not differ by body fat, but newborns born with high body fat show depressed baroreflex sensitivity.

New charts for the assessment of body composition, according to air-displacement plethysmography, at birth and across the first 6 mo of life

BACKGROUND

Air-displacement plethysmography (ADP) is a good candidate for monitoring body composition in newborns and young infants, but reference centile curves are lacking that allow for assessment at birth and across the first 6 mo of life.

OBJECTIVE

Using pooled data from 4 studies, we aimed to produce new charts for assessment according to gestational age at birth (30 + 1 to 41 + 6 wk) and postnatal age at measurement (1-27 wk).

METHODS

The sample comprised 222 preterm infants born in the United States who were measured at birth; 1029 term infants born in Ireland who were measured at birth; and 149 term infants born in the United States and 57 term infants born in Italy who were measured at birth, 1 and 2 wk, and 1, 2, 3, 4, 5, and 6 mo of age. Infants whose birth weights were <3rd or >97th centile of the INTERGROWTH-21st standard were excluded, thereby ensuring that the charts depict body composition of infants whose birth weights did not indicate suboptimal fetal growth. Sex-specific centiles for fat mass (kg), fat-free mass (kg), and percentage body fat were estimated using the lambda-mu-sigma (LMS) method.

RESULTS

For each sex and measure (e.g., fat mass), the new charts comprised 2 panels. The first showed centiles according to gestational age, allowing term infants to be assessed at birth and preterm infants to be monitored until they reached term. The second showed centiles according to postnatal age, allowing all infants to be monitored to age 27 wk. The LMS values underlying the charts were presented, enabling researchers and clinicians to convert measurements to centiles and z scores.

CONCLUSIONS

The new charts provide a single tool for the assessment of body composition, according to ADP, in infants across the first 6 mo of life and will help enhance early-life nutritional management.

Fat trajectory after birth in very preterm infants mimics healthy term infants

BACKGROUND

Infants born very preterm experience poor postnatal growth relative to intrauterine growth, but at term equivalent age, they have increased percentage body fat compared with infants born at term.

OBJECTIVES

The aim of this study was to assess body composition in very preterm infants born before 32 weeks postmenstrual age and to compare this with infants born at 32-36 weeks of gestation.

METHODS

Percentage fat, fat mass and fat-free mass were measured in 87 very preterm infants born <32 weeks of gestation and studied at 32-36 weeks and in 88 control infants born at 32-36 weeks of gestation and measured on days 2-5 postnatally.

RESULTS

At 32-36 weeks, very preterm infants were lighter and shorter, had significantly greater percentage fat and absolute fat mass and had a significantly lower absolute fat-free mass than the control group. The trajectory in percentage fat over increasing postnatal age in very preterm infants was closely aligned to that in term infants.

CONCLUSIONS

Infants born very preterm accumulate fat rapidly after birth and have a deficit in fat-free mass. Fat accumulation may be triggered by birth or associated events. If this rapid fat accretion is not taken into account, assessment of growth based on weight alone will underestimate the deficit in fat-free mass.

Measuring body composition in the preterm infant: Evidence base and practicalities

Preterm birth and body composition have demonstrable effects on growth and later health outcomes. Preterm infants reach term equivalent age with a lower proportion of lean mass and higher body fat percentage than their term equivalent counterparts. Weight and length do not give an accurate assessment of body composition. Tracking body composition rather than just weight is a fundamental part of improving nutritional outcomes. This is important given the ongoing controversies regarding the nutritional needs of preterm infants, as well as establishing suitable targets for their growth. In this review we describe current methodologies used in the measurement of body composition of the preterm infant and the review the recent published evidence for their accuracy and utility. Current measurement techniques employed include air displacement plethysmography, bioelectrical impedance analysis, isotope dilution techniques, MRI and a combination of manual measurements including skinfold thickness, body mass index and mid upper arm/mid-thigh circumference. These measures allow for the estimation of fat mass, fat-free mass and regional assessment of adiposity. Some methods, such as dual-energy X-ray absorptiometry and air displacement plethysmography do allow for comparison of change in body composition over time in cohorts of preterm infants that may be studied over a longer period of time and into adult life. However, none of the currently described methods give an accurate and practically achievable method of obtaining body composition measures in preterm infants in day to day routine clinical practise, although this remains a key priority when decisions are being made about how best to feed.

Early body composition changes are associated with neurodevelopmental and metabolic outcomes at 4 years of age in very preterm infants

BACKGROUND

Very preterm (VPT) infants are at-risk for altered growth, slower speed of processing (SOP), and hypertension. This study assesses the relationship between postnatal body composition (BC), neurodevelopment (indexed by SOP), and blood pressure (BP) in VPT infants.

METHODS

Thirty-four VPT infants underwent weekly measurements and BC testing until discharge and post-discharge at 4 mos CGA and 4 yrs. At post-discharge visits, SOP was assessed using visual evoked potentials and the NIH Toolbox; BP was also measured.

RESULTS

In-hospital rate of weight, length and fat-free mass (FFM) gains were associated with faster SOP at 4 yrs. Higher rate of gains in weight and FFM from discharge to 4 mos CGA were associated with faster SOP at 4 mos CGA, while higher fat mass (FM) gains during the same time were positively associated with BP at 4 yrs. BC at 4 yrs nor gains beyond 4 mos CGA were associated with outcomes.

CONCLUSIONS

In VPT infants, early FFM gains are associated with faster SOP, whereas post-discharge FM gains are associated with higher BPs at 4 yrs. This shows birth to 4 mos CGA is a sensitive period for growth and its relation to neurodevelopmental and metabolic outcomes. Close monitoring and early nutritional adjustments to optimize quality of gains may improve outcomes.

Growth and body composition in preterm newborns with bronchopulmonary dysplasia: a cohort study

Objective To compare growth and body composition of preterm infants (gestational age <32 weeks) with and without bronchopulmonary dysplasia (BPD). Methods A prospective cohort involving three neonatal units in the public health system of the Brazilian city of Rio de Janeiro. Inclusion: newborns with gestational age <32 weeks.

EXPOSURE

BPD. Anthropometric measurements were performed at birth and at 1 month of infant corrected age. Body composition was measured using an air displacement plethysmography (ADP) (PEA POD®) at 1 month of infant corrected age. Results Ninety-five newborns were eligible, of which 67 were included, 32.8% of them with BPD. Newborns with BPD presented lower gestational age at birth, greater need for resuscitation in the delivery room, received parenteral nutrition (PN) for a longer period of time, achieved lower weights during hospital stay and required more time to reach a full enteral diet. No statistically significant differences were observed in relation to anthropometric measurements and body composition at 1 month of infant corrected age between the groups with and without BPD. Conclusion This study, unlike previous ones, has shown that children who developed BPD were able to regain growth, as measured by anthropometric measures, with no change in body composition at 1 month of infant corrected age.

Body composition in preterm infants with intrauterine growth restriction: a cohort study

Aims:

The comparison of body composition parameters between the small for gestational age (SGA) and appropriate for gestational age (AGA) at term, 1, 3 and 5 months corrected ages in very preterm infants.

Methods:

This cohort study included 92 preterm infants at term age, younger than 32 weeks or <1500 g, classified in two groups: SGA and AGA. Anthropometry and body composition, estimated by air displacement plethysmography, were evaluated at the corrected ages: term and 1, 3, and 5 months. We used the lean mass/fat mass index (LM/FM) at each time point and the weight, length and head circumference SDS gain between the time points.

Results:

At term age, the SGA preterm infants had less lean mass (g), fat mass (g) and percent fat mass but a greater LM/FM index than AGA infants (P<0.001). At 1 month corrected age the LM/FM index and percent fat mass between the groups became similar. Lower lean mass persisted up to 3 months in the SGA group [4004 g (3256–4595) vs. 4432 g (3190–6246), P<0.001]. During the first month corrected age, the weight SDS gain was higher in SGA preterm infants when compared to AGA preterm infants. However, the SGA preterm infants remained lighter, shorter and with smaller head circumferences than the AGA preterm infants until 3 months of corrected age.

Conclusions:

The greater lean tissue deficits and an earlier “catch-up” in fat in the SGA group can reflect growth patterns variability since the early life.

Body Fatness and Cardiovascular Health in Newborn Infants

Birth weight is associated with cardiovascular disease, with those at both ends of the spectrum at increased risk. However, birth weight is a crude surrogate of fetal growth. Measures of body composition may more accurately identify high risk infants. We aimed to determine whether aortic wall thickening, cardiac autonomic control, and cardiac structure/function differ in newborns with high or low body fatness compared to those with average body fatness. 189 healthy singleton term born neonates were recruited and stratified by body fat percentiles (sex and gestation-specific). Infants with low body fat had higher aortic intima-media thickness (43 µm (95% confidence interval (CI) 7, 78), p = 0.02), lower heart rate variability (log total power, -0.5 (95% CI -0.8, -0.1), p = 0.008), and thicker ventricular walls (posterior wall thickness, 3.1 mm (95% CI 1.6, 4.6), p < 0.001) compared to infants with average body fatness. Infants with high body fat showed no differences in aortic intima-media thickness (-2 µm (95% CI -37, 33), p = 0.91) or cardiac structure compared to average body fatness, although stroke volume (-0.3 mL/kg (95% CI -0.6, -0.0), p = 0.003) and heart rate variability were lower (log total power, -0.8 (95% CI -1.1, -0.5), p < 0.001). The non-linear association of body fatness with heart rate variability was independent of birth weight. Infants born with low or high body fat have altered markers of cardiovascular health. Assessment of body fatness alongside birth weight may assist in identifying high risk individuals.

Air displacement plethysmography (pea pod) in full-term and pre-term infants: a comprehensive review of accuracy, reproducibility, and practical challenges

Air displacement plethysmography (ADP) has been widely utilised to track body composition because it is considered to be practical, reliable, and valid. Pea Pod is the infant version of ADP that accommodates infants up to the age of 6 months and has been widely utilised to assess the body composition of full-term infants, and more recently pre-term infants. The primary goal of this comprehensive review is to 1) discuss the accuracy/reproducibility of Pea Pod in both full- and pre-term infants, 2) highlight and discuss practical challenges and potential sources of measurement errors in relation to Pea Pod operating principles, and 3) make suggestions for future research direction to overcome the identified limitations.

An overview of assessment methodology for obesity-related variables in infants at risk

BACKGROUND

The first 2 years of a child's life are a particularly critical time period for obesity prevention.

AIM

An increasing amount of research across the world is aimed at understanding factors that impact early childhood obesity and developing interventions that target these factors effectively. With this growing interest, new and interdisciplinary research teams are developing to meet this research need. Due to rapid growth velocity during this phase of the lifespan, typical assessments used in older populations may not be valid or applicable in infants, and investigators need to be aware of the pros and cons of specific methodological strategies.

METHODS

This paper provides an overview of methodology available to assess obesity-related factors in the areas of anthropometry and body composition, nutrient intake, and energy expenditure in infants aged 0-2 years.

RESULTS

Gold standard measures for body composition, such as dual-energy X-ray absorptiometry (DXA) or other imaging techniques, are costly, require highly trained personnel, and are limited for research application. Nutrient intake methodology primarily includes surveys and questionnaires completed via parent proxy report. In terms of energy expenditure, methods of calorimetry are expensive and may not differentiate between different activities. Questionnaires or physical activity sensors offer another way of energy expenditure assessment. However, questionnaires have a certain recall bias, while the sensors require further validation.

CONCLUSIONS

Overall, in addition to understanding the pros and cons of each assessment tool, researchers should take into consideration the experience of the interdisciplinary team of investigators, as well as the cost and availability of measures at their institution.

High-resolution rapid neonatal whole-body composition using 3.0 Tesla chemical shift magnetic resonance imaging

BackgroundTo evaluate a whole-body rapid imaging technique to calculate neonatal lean body mass and percentage adiposity using 3.0 Tesla chemical shift magnetic resonance imaging (MRI).MethodsA 2-Point Dixon MRI technique was used to calculate whole-body fat and water images in term (n=10) and preterm (n=15) infants.ResultsChemical shift images were obtained in 42 s. MRI calculated whole-body mass correlated closely with measured body weight (R²=0.87; P<0.001). Scan-rescan analysis demonstrated a 95% limit of agreement of 1.3% adiposity. Preterm infants were born at a median of 25.7 weeks' gestation with birth weight 840 g. At term-corrected age, former preterm infants were lighter than term-born controls, 2,519 vs. 3,094 g regressing out age and group as covariates (P=0.005). However, this was not because of reduced percentage adiposity 26% vs. 24% (P=0.28). At term-corrected age, former preterm infants had significantly reduced lean body mass compared with that of term-born controls 1,935 vs. 2,416 g (P=0.002).ConclusionRapid whole-body imaging for assessment of lean body mass and adiposity in term and preterm infants is feasible, accurate, and repeatable. Deficits in whole-body mass in former preterm infants at term-corrected age are due to reductions in lean body mass not due to differences in adiposity.

Is the body composition development in premature infants associated with a distinctive nuclear magnetic resonance metabolomic profiling of urine?

OBJECTIVE

Preterm infants' body composition at term-corrected age differs from that of term infants but appears to be similar at the age of 3 months. The aim of this study was to compare the metabolomic pattern of preterm infants at term and at 3 months with that of term infants and to determine its association with body composition development.

METHOD

We designed a pilot study. Growth and body composition were evaluated by an air displacement plethysmography system in 13 preterm infants and seven term newborns at term and at 3 months of corrected age. Urine samples were collected at the same time points and analysed by nuclear magnetic resonance.

RESULTS

At term-corrected age, preterm infants showed a higher fat mass percentage compared with that of term newborns, whereas at 3 months of corrected age, the body composition parameters were similar between the groups. At the first time point, nuclear magnetic resonance analysis showed a urinary increase in choline/phosphocholine, betaine and glucose in preterm infants. At the second time point, the preterm group exhibited a urinary increase in choline/phosphocholine and a decrease in betaine.

CONCLUSIONS

The increased urinary excretion of choline, a betaine precursor, could reflect a potential altered metabolism in preterm infants.

Clinical evaluation of two different protein content formulas fed to full-term healthy infants: a randomized controlled trial

BACKGROUND

A high early protein intake is associated with rapid postnatal weight gain and altered body composition. We aimed to evaluate the safety of a low-protein formula in healthy full-term infants.

METHODS

A randomized controlled trial was conducted. A total of 118 infants were randomized to receive two different protein content formulas (formula A or formula B (protein content: 1.2 vs. 1.7 g/100 mL, respectively)) for the first 4 months of life. Anthropometry and body composition by air displacement plethysmography were assessed at enrolment and at two and 4 months. The reference group comprised 50 healthy, exclusively breastfed, full-term infants.

RESULTS

Weight gain (g/day) throughout the study was similar between the formula groups (32.5 ± 6.1 vs. 32.8 ± 6.8) and in the reference group (30.4 ± 5.4). The formula groups showed similar body composition but a different fat-free mass content from breastfed infants at two and 4 months. However, the formula A group showed a fat-free mass increase more similar to that of the breastfed infants. The occurrence of gastrointestinal symptoms or adverse events was similar between the formula groups.

CONCLUSIONS

Feeding a low-protein content formula appears to be safe and to promote adequate growth, although determination of the long-term effect on body composition requires further study.

TRIAL REGISTRATION

The present study was retrospectively registered in ClinicalTrials.gov (trial number: NCT03035721 on January 18, 2017).

Protein use and weight-gain quality in very-low-birth-weight preterm infants fed human milk or formula

Background

Nutritional management of preterm infants aims to approximate the tissue growth and body composition of a fetus of the same postmenstrual age. The adequacy of the quality of protein supply can influence the rate and the relative quality of weight gain.

Objective

We investigated the protein balance according to feeding regimen and the association between human milk feeding and fat-free mass content at the term-corrected age in very-low-birth-weight preterm infants.

Design

A prospective observational study was conducted. Inclusion criteria were as follows: healthy infants, gestational age ≤32 wk, birth weight <1500 g, stable clinical conditions, and feeding by mouth with human milk or formula at discharge. Infants were enrolled at hospital discharge. At enrollment, macronutrient intakes and protein balance were determined. Anthropometric measurements and body composition were also assessed. The nutritional composition of human milk was calculated by infrared spectroscopy. The protein balance was determined according to the nitrogen balance standard method. Body composition was assessed by an air-displacement plethysmography system. At the term-corrected age, anthropometry and body composition assessments were repeated.

Results

Seventeen preterm infants fed fortified human milk and 15 preterm infants fed formula were enrolled. At discharge, despite similar macronutrient intakes, infants fed fortified human milk showed a higher nitrogen balance (expressed as mg · kg-1 · d-1) compared with preterm formula-fed infants (mean ± SD: 488.3 ± 75 compared with 409.8 ± 85 mg · kg-1 · d-1, P = 0.009). At term-corrected age, growth was similar in the 2 groups, whereas fortified human milk-fed infants showed a higher percentage of fat-free mass (85.1% ± 2.8% compared with 80.8% ± 3.2%, P = 0.002). Moreover, at multiple linear regression, fat-free mass content was independently associated with being fed human milk (R2 = 0.93, P < 0.0001).

Conclusion

Our findings suggest that human milk feeding is associated with early fat-free mass deposition in healthy and stable preterm infants. This trial was registered at www.clinicaltrials.gov as NCT03013374.

Growth and body composition of preterm infants less than or equal to 32 weeks: Cohort study

BACKGROUND

Extremely preterm infants with weights less than the 10th percentile at discharge have a fat-free mass deficit.

AIM

To analyze the relationship of weight Z-scores less than -2SD at term age with fat-free mass and fat mass at term age and at 1 and 3 months of corrected age in very preterm infants.

STUDY DESIGN

COHORT STUDY: Subjects: Sixty-six preterm infants born before or at 32 weeks gestation with birth weight equal or greater than the 10th percentile for age were included at term age. They were classified according to weight Z-score as either: "term (-)" (n = 18) if weight Z-scores were less -2SD or "term (+)" (n = 48) if the weight Z-scores were equal or greater than -2SD at term age.

OUTCOME MEASURES

Growth and body composition by an air displacement plethysmography system and bioimpedance were assessed at term age and 1 and 3 months of corrected age.

RESULTS

Lower fat-free mass persisted up to 3 months in the "term (-)" group [4137 g (645) vs 4592 g (707), p < .01]. Fat mass was lower in the "term (-)" group at term and at 1 month but was similar at 3 months of corrected age [1295 g (774) vs 1477 g (782), p = .109]. Weight, length and head circumference Z-scores were lower in the "term (-)" group compared to those in the "term (+)" group.

CONCLUSIONS

The lean tissue deficits were maintained in the "term (-)" group while the differences in body fat percentage were not.

No effect of adding dairy lipids or long chain polyunsaturated fatty acids on formula tolerance and growth in full term infants: a randomized controlled trial

Background

When breastfeeding is not possible, infants are fed formulas in which lipids are usually of plant origin. However, the use of dairy fat in combination with plant oils enables a lipid profile in formula closer to breast milk in terms of fatty acid composition, triglyceride structure and cholesterol content. The objectives of this study were to investigate the impact on growth and gastrointestinal tolerance of a formula containing a mix of dairy lipids and plant oils in healthy infants.

Methods

This study was a monocentric, double-blind, controlled, randomized trial. Healthy term infants aged less than 3 weeks whose mothers did not breastfeed were randomly allocated to formula containing either: a mix of plant oils and dairy fat (D), only plant oils (P) or plant oils supplemented with long-chain polyunsaturated fatty acids (PDHA). Breastfed infants were included in a reference group (BF). Anthropometric parameters and body composition were measured after 2 and 4 months. Gastrointestinal tolerance was evaluated during 2 day-periods after 1 and 3 months thanks to descriptive parameters reported by parents. Nonrandomized BF infants were not included in the statistical analysis.

Results

Eighty eight formula-fed and 29 BF infants were enrolled. Gains of weight, recumbent length, cranial circumference and fat mass were similar between the 3 formula-fed groups at 2 and 4 months and close to those of BF. Z-scores for weight, recumbent length and cranial circumference in all groups were within normal ranges for growth standards. No significant differences were noted among the 3 formula groups in gastrointestinal parameters (stool frequency/consistency/color), occurrence of gastrointestinal symptoms (abdominal pain, flatulence, regurgitation) or infant’s behavior.

Conclusions

A formula containing a mix of dairy lipids and plant oils enables a normal growth in healthy newborns. This formula is well tolerated and does not lead to abnormal gastrointestinal symptoms. Consequently, reintroduction of dairy lipids could represent an interesting strategy to improve lipid quality in infant formulas.

Trial registration

ClinicalTrials.gov Identifier NCT01611649, retrospectively registered on May 25, 2012.

Body Composition Changes from Infancy to 4 Years and Associations with Early Childhood Cognition in Preterm and Full-Term Children

BACKGROUND

Infants born prematurely are at risk for neurodevelopmental complications. Early growth is associated with improved later cognition. The relationship of early proportionality and body composition with later cognition is not well established.

OBJECTIVES

To assess differences in fat-free mass and adiposity (fat mass, percent body fat) changes in preterm and full-term infants through preschool age and examine associations with early childhood cognition.

METHODS

This is a prospective, observational study in an appropriate for gestational age cohort of 71 patients (20 preterm and 51 full-term) from infancy through preschool age. Anthropometric and body composition measurements via air displacement plethysmography were obtained during infancy at term and 3-4 months (preterm corrected ages), and at 4 years. Cognitive testing occurred at 4 years. Associations of body composition changes between visits with cognitive function were tested using linear regression.

RESULTS

In the preterm group, higher term to 4-month corrected age percent body fat gains were associated with lower working memory performance (p = 0.01), and higher 4-month corrected age to 4-year fat-free mass gains were associated with higher full-scale IQ (p = 0.03) and speed of processing performance (p ≤ 0.02). In the full-term group, higher 4-month to 4-year fat mass gains were associated with lower full-scale IQ (p = 0.03).

CONCLUSIONS

Body composition gains during different time periods are associated with varying areas of cognitive function. These findings may inform interventions aimed at optimal growth.

Do changing levels of maternal exercise during pregnancy affect neonatal adiposity? Secondary analysis of the babies after SCOPE: evaluating the longitudinal impact using neurological and nutritional endpoints (BASELINE) birth cohort (Cork, Ireland)

OBJECTIVE

To investigate whether changing levels of exercise during pregnancy are related to altered neonatal adiposity.

DESIGN

Secondary analysis of data from a prospective cohort study.

SETTING

Cork, Ireland.

PARTICIPANTS

1200 mother - infant pairs recruited as part of a prospective birth cohort, Babies After SCOPE: Evaluating the Longitudinal Impact Using Neurological and Nutritional Endpoints (BASELINE).

MAIN OUTCOME MEASURES

Neonatal adiposity was assessed within several days of birth using air displacement plethysmography (PEAPOD). Per cent body fat (BF%) as a continuous outcome and a pair of dichotomous variables; high or low adiposity, representing BF% >90th or <10th centile, respectively. Multivariable linear and logistic regression models were used to investigate the relationship between exercise and the respective outcomes.

RESULTS

Crude analysis revealed no association between a changing level of exercise (since becoming pregnant) at 15 weeks' gestation and any of the outcomes (BF%, low adiposity and high adiposity). At 20 weeks' gestation, analyses revealed that relative to women who do not change their exercise level up to 20 weeks, those women who decreased their exercise level were more likely to give birth to a neonate with adiposity above the 90th centile (OR 1.62, 95% CI 1.07 to 2.46). This association was maintained after adjustment for putative confounders (OR 1.62, 95% CI 1.06 to 2.47).

CONCLUSIONS

We observed a possible critical period for the association between changing exercise levels and neonatal adiposity, with no association observed with exercise recall for the first 15 weeks of gestation, but an association with a decreasing level of exercise between 15 and 20 weeks. These results should be interpreted in line with the limitations of the study and further studies utilising objectively measured estimates of exercise are required in order to replicate these findings.

TRIAL REGISTRATION NUMBER

NCT01498965.

Do anthropometric measures accurately reflect body composition in preterm infants?

BACKGROUND

Recent literature suggests that neonatal adiposity is predictive of later metabolic health, while neonatal lean mass is predictive of later cognitive function amongst preterm infants. Anthropometric indices that accurately reflect neonatal body composition could improve clinical care and aid future research, but their validity has not been systematically tested in preterm infants.

OBJECTIVE

To determine the weight/length indices that best reflect neonatal body composition in preterm infants.

METHODS

Weight and length were measured, and body composition (fat-free mass (FFM), fat mass (FM) and percent body fat (%BF)) was assessed using air-displacement plethysmography within 72 h of birth in 218 preterm infants. The best weight/length proxy for FFM, FM and %BF were those with the highest proportion variance explained (R² ) and lowest root mean square error (RMSE) in linear regression models.

RESULTS

Among all of the weight/length indices tested, weight/length² was the best proxy for %BF, but nonetheless exhibited very low variance explained (R²  = 0.27) and high prediction error (RMSE = 3.5% fat). Body weight unadjusted for length was strongly associated with FFM (R²  = 0.97).

CONCLUSIONS

No weight/length index accurately reflected %BF. Weight/length indices are not appropriate for assessment of relative adiposity in preterm infants near birth. What's known on this subject: Compared with term infants, preterm infants have increased fat mass and diminished fat-free mass upon hospital discharge. Early adiposity predicts later metabolic health, while early lean mass is predictive of later neurodevelopmental outcomes. Optimal anthropometric proxies for preterm body composition at birth are not established.

WHAT THIS STUDY ADDS

Weight is an adequate surrogate for lean mass at birth in preterm infants. There are no weight/length indices that accurately reflect neonatal adiposity at birth.

Body Composition Trajectories From Infancy to Preschool in Children Born Premature Versus Full-term

OBJECTIVES

The aim of the study was to longitudinally characterize infancy to preschool body composition trajectories and the association of early fat and fat-free mass gains with preschool age body composition in children born premature versus full-term.

METHODS

A cohort of appropriate-for-gestational age preterm (n = 20) and term (n = 51) infants were followed at 3 visits: "neonatal" visit 1 at 2 weeks of age for term and near term corrected age for preterm; "infancy" visit 2 at 3 to 4 months (preterm corrected age); "preschool" visit 3 at 4 years. Body composition via air displacement plethysmography and anthropometrics were measured at all visits. Tracking of infancy weight and body composition with preschool measurements was tested using Pearson partial correlation coefficients. Associations between serial body composition measurements were assessed using multiple linear regression.

RESULTS

Early differences in body composition between premature (mean gestational age 31.9 weeks, mean birth weight 1843 g) and full-term (mean gestational age 39.8 weeks) infants were not present at preschool age. Visit 1 body composition was not correlated with preschool measurements in the preterm infants. Visit 2 measurements were correlated with preschool measures. Fat-free mass accretion from visit 1 to visit 2 was positively associated with preschool lean mass (β = 0.038, P = 0.049) in preterm children, whereas fat accretion was not associated with preschool body composition.

CONCLUSIONS

Children born prematurely and full-term have similar body composition at preschool age. For preterms infancy fat-free mass gains, and not adiposity gains, are positively associated with preschool fat-free mass; this may be associated with lower risk of later obesity and adverse metabolic outcomes.