Body composition reference charts for infants from birth to 24 months: Multicenter Infant Body Composition Reference Study

Exploring Infant Size and Body Composition at 18 Months: An Ambidirectional Peri-Urban South African Cohort Study

The first 1000 days of life lay the foundations for subsequent growth. This ambidirectional study, including prenatal, perinatal and postnatal factors, aimed to identify exposure variables affecting body size and composition and corresponding Z-score outcomes at age 18 months in infants born to women at low risk of adverse pregnancy outcomes in a peri-urban area of South Africa. Prenatal factors (maternal age, HIV status, anthropometry, parity, food insecurity and umbilical artery resistance index Z-score (UmA-RIAZ) as a measure of placental function, with higher UmA-RIAZ indicating poorer placental function); perinatal factors (infant sex, gestational age and birth anthropometry) and postnatal factors (infant feeding) were included as exposure variables, with infant anthropometry and body composition at 18 months as outcomes. Simple linear regression analysis was used to investigate associations between exposure variables and infant outcomes, and variables with p < 0.10 were included in the subsequent multiple regression analyses. Multiple regression analysis showed that higher UmA-RIAZ predicted lower birthweight [-0.11 kg (95% CI: -0.17, -0.04 kg)], birthweight-for-age Z-score [-0.24 (95% CI: -0.39, -0.09)] and 18-month infant length [-0.9 cm (95% CI: -1.4, -0.4 cm)] and length-for-age Z-score [-0.28 (95% CI: -0.45, -0.11)]. Maternal HIV infection predicted reduced 18-month infant length-for-age Z-score [-0.46 (95% CI: -0.83, -0.09)]. Household food insecurity predicted reduced fat-free mass-for-age Z-score at 18 months [-0.27 (95% CI: -0.51, -0.03)]. Infant anthropometry and body composition outcomes, therefore, are greatly affected by pre- and postnatal nutrition-related factors, such as placental insufficiency in utero and household food insecurity, with long-term consequences including stunting, which impact the individual, future generations and society.

Bioelectrical impedance vector (BIVA) reference values for healthy term newborns 1-2 days old

BACKGROUND

Bioelectrical impedance vector analysis (BIVA) is a valuable tool for assessing individuals' body fluids and nutritional status by examining the impedance vector's position on the mean reference impedance vector tolerance ellipses from healthy populations. Nevertheless, differences in BIVA tolerance ellipses have been reported between populations with different ethnicities, body mass index (BMI), sex, and age.

AIM

To construct BIVA reference values for healthy newborns aged 1-2 days born to term and compare them to those previously reported for newborns from different populations.

METHODS

A cross-sectional study was conducted using bioelectrical impedance data collected within the first 48 h after birth from healthy, term newborns with healthy mothers. The mean impedance vector 50 %, 75 %, and 95 % tolerance ellipses were constructed and compared with those previously reported for other newborn populations.

RESULTS

The healthy newborns' mean impedance vector showed significant differences between populations, with similarities observed only between our newborn population and one of the four previously reported populations. No vector displacement was found related to the mode of delivery or sex of the newborns.

CONCLUSIONS

The mean impedance vector tolerance ellipses for healthy term newborn population aged 1-2 days were constructed. Our results show that there are differences in the mean impedance vector compared to other BIVA newborn studies, which could result from the influence of ethnic background on BIVA tolerance ellipses or be due to differences in the technique for BIA assessment.

The proportion of weight gain due to change in fat mass in infants with vs without rapid growth

BACKGROUND

There is extensive evidence that rapid infant weight gain increases the risk of childhood obesity, but this is normally based on childhood body mass index (BMI) only and whether or not this is because infants with rapid weight gain accrue greater fat mass is unknown.

OBJECTIVE

The primary objective of our study was to test whether the proportion of infant weight gain due to concurrent increases in fat mass is greater in infants with rapid weight gain as compared to those with normal growth.

METHODS

Body composition was assessed by (1) air-displacement plethysmography (ADP) at 0 and 6 months in 342 infants from Australia, India, and South Africa and (2) deuterium dilution (DD) at 3 and 24 months in 555 infants from Brazil, Pakistan, South Africa, and Sri Lanka. Weight gain and length growth were each categorized as slow, normal, or rapid using cut-offs of <-0.67 or >+0.67 Z-scores. Regression was used to estimate and contrast the percentages of weight change due to fat mass change.

RESULTS

Approximately 40% of the average weight gain between 0 and 6 months and 20% of the average weight gain between 3 and 24 months was due to increase in fat mass. In both samples, compared to the normal group, the proportion of weight gain due to fat mass was higher on average among infants with rapid weight gain and lower among infants with slow weight gain, with considerable individual variability. Conversely, slow and rapid length growth was not associated with differential gains in fat mass.

CONCLUSIONS

Pediatricians should monitor infant growth with the understanding that, while crossing upward through the weight centiles generally is accompanied by greater adiposity gains (not just higher BMI), upward crossing through the length centiles is not.

Body Composition Changes and Associations in Infants and Mothers During the First Year: Insights from a Pilot Study of the Baby-bod Project

BACKGROUND

The period following childbirth is marked by dynamic changes in maternal physiology and the growth trajectory of the newborn. We aimed to elucidate the changes and associations in body composition of infants and their mothers during the first year postpartum.

METHODS

This pilot study assessed infant body composition using the PEA POD air displacement plethysmography (ADP) system (birth-6 months) and deuterium dilution (9-12 months). Maternal body composition was assessed using the BOD POD ADP system at 12 months postpartum. Mothers were grouped by prepregnancy body mass index (BMI) <25 kg/m2 (lean) or ≥25 kg/m2 (overweight/obese: OW/OB), and data were analysed using linear regression.

RESULTS

Twenty-nine infant-mother pairs were assessed. Infant percent fat mass (%FM) increased from birth to 6 months (9.3% vs. 24.2%; p < 0.001) and then gradually declined. At birth and 3 months, %FM was significantly higher in infants born to OW/OB mothers compared to their lean counterparts. A significant positive association (β = 0.3; p = 0.040) was observed between maternal %FM and infant %FM at 1 year post-delivery after controlling for the mother's prepregnancy BMI.

CONCLUSIONS

Infants born to OW/OB mothers have increased %FM at birth and 3 months, which may have consequences for their health throughout childhood and into adulthood. Moreover, maternal prepregnancy BMI is a significant predictor of maternal postpartum weight status and body composition and impacts the relationship between maternal and infant body composition at 12 months postpartum. While the findings of our pilot study underscore the importance of encouraging women of childbearing age to maintain a healthy BMI before conception, further research is needed to substantiate these results.

Body Composition in Preterm Infants: Current Insights and Emerging Perspectives

In recent years, significant advancements in respiratory and nutritional care have markedly improved the survival rates of preterm infants and enhanced long-term health outcomes. Despite these improvements, emerging research highlights the lasting impacts of early growth patterns on an individual's health trajectory. Adults born prematurely face a higher incidence of health issues related to their early birth. The American Academy of Pediatrics recommends that preterm infants should achieve growth rates similar to those of fetuses, with clinicians emphasizing nutrition delivery to help these infants reach their expected weight for gestational age. However, this approach often results in altered body composition, characterized by increased fat mass and decreased fat-free mass compared to full-term infants. Air displacement plethysmography stands out as a highly reliable method for measuring preterm body composition, while DEXA scans, despite their reliability, tend to overestimate body fat. Other methods include bioelectric impedance, isotope dilution, MRI, ultrasound, and skinfold thickness, each with its own strengths and limitations. In this paper, we aim to raise awareness among neonatal clinicians about the importance of achieving acceptable neonatal body composition. We discuss the pros and cons of different body composition measurement methods, the impact of nutrition and other factors on body composition in preterm infants, long-term follow-up data, and the potential use of body composition data to tailor nutritional interventions in NICU and post-discharge settings. This comprehensive approach is designed to optimize health outcomes for preterm newborns by focusing on their body composition from an early stage.

Fetal body composition reference charts and sexual dimorphism using magnetic resonance imaging

BACKGROUND

The American Academy of Pediatrics advises that the nutrition of preterm infants should target a body composition similar to that of a fetus in utero. Still, reference charts for intrauterine body composition are missing. Moreover, data on sexual differences in intrauterine body composition during pregnancy are limited.

OBJECTIVES

The objective of this study was to create reference charts for intrauterine body composition from 30 to 36+6 weeks postconception and to evaluate the differences between sexes.

METHODS

In this single-center retrospective study, data from 197 normal developing fetuses in late gestation was acquired at 3T magnetic resonance imaging (MRI) scans, including True Fast Imaging with Steady State Free Precession and T1-weighted 2-point Dixon sequences covering the entire fetus. Deep convolutional neural networks were utilized to automatically segment the fetal body and subcutaneous adipose tissue. The fetus's body mass (BM), fat signal fraction (FSF), fat mass (FM), FM percentage (FM%), fat-free mass (FFM), and FFM percentage (FFM%) were calculated. Using the Generalized Additive Models for Location, Scale, and Shape (GAMLSS) method, reference charts were created, and sexual dimorphism was examined using analysis of covariance (ANCOVA). A P value <0.05 was deemed significant.

RESULTS

Throughout late gestation, BM, FSF, FM, FM%, and FFM increased, while the FFM% decreased. Reference charts for gestational age and sex-specific percentiles are provided. Males exhibited significantly higher BM (7.2%; 95% confidence interval [95% CI]: 1.9, 12.4), FFM (8.8%; 95% CI: 5.8, 11.9), and FFM% (1.7%; 95% CI: 1, 2.4) and lower FSF (-3.6%; 95% CI: -5.6, -1.8) and FM% (-1.7%; 95% CI: -2.4, -1), (P < 0.001) compared with females, with no significant difference in FM between sexes (P = 0.876).

CONCLUSIONS

MRI-derived intrauterine body composition growth charts are valuable for tracking growth in preterm infants. This study demonstrated that sexual differences in body composition are already present in the intrauterine phase.

Anthropometric prediction models of body composition in 3 to 24month old infants: a multicenter international study

BACKGROUND

Accurate assessment of body composition during infancy is an important marker of early growth. This study aimed to develop anthropometric models to predict body composition in 3-24-month-old infants from diverse socioeconomic settings and ethnic groups.

METHODS

An observational, longitudinal, prospective, multi-country study of infants from 3 to 24 months with body composition assessed at three monthly intervals using deuterium dilution (DD) and anthropometry. Linear mixed modelling was utilized to generate sex-specific fat mass (FM) and fat-free mass (FFM) prediction equations, using length(m), weight-for-length (kg/m), triceps and subscapular skinfolds and South Asian ethnicity as variables. The study sample consisted of 1896 (942 measurements from 310 girls) training data sets, 941 (441 measurements from 154 girls) validation data sets of 3-24 months from Brazil, Pakistan, South Africa and Sri Lanka. The external validation group (test) comprised 349 measurements from 250 (185 from 124 girls) infants 3-6 months of age from South Africa, Australia and India.

RESULTS

Sex-specific equations for three age categories (3-9 months; 10-18 months; 19-24 months) were developed, validated on same population and externally validated. Root mean squared error (RMSE) was similar between training, validation and test data for assessment of FM and FFM in boys and in girls. RMSPE and mean absolute percentage error (MAPE) were higher in validation compared to test data for predicting FM, however, in the assessment of FFM, both measures were lower in validation data. RMSE for test data from South Africa (M/F-0.46/0.45 kg) showed good agreement with validation data for assessment of FFM compared to Australia (M/F-0.51/0.33 kg) and India(M/F-0.77/0.80 kg).

CONCLUSIONS

Anthropometry-based FFM prediction equations provide acceptable results. Assessments based on equations developed on similar populations are more applicable than those developed from a different population.

Infant growth and body composition from birth to 24 months: are infants developing the same?

BACKGROUND

Given the importance of infancy for establishing growth trajectories, with later-life health consequences, we investigated longitudinal body composition among infants from six economically and ethnically diverse countries.

METHODS

We recruited mother-infant dyads using the WHO Multicenter Growth Reference Study criteria. We measured fat-free mass (FFM) in 1393 (49% female) infants from birth to 6 months of age (Australia, India, and South Africa; n = 468), 3-24 months of age (Brazil, Pakistan, South Africa, and Sri Lanka; n = 925), and derived fat mass (FM), fat mass index (FMI), and fat-free mass index (FFMI). Height-for-age (HAZ), weight-for-age (WAZ), and weight-for-length (WHZ) Z-scores were computed. Sex differences were assessed using a t-test, and country differences using a one-way analysis of covariance. We further compared subsamples of children with average (-0.25 > HAZ < +0.25), below-average (≤-0.25) and above-average (≥+0.25) HAZ.

RESULTS

HAZ performed well between 0 and 6 months, but less so between 3 and 24 months. The stunting prevalence peaked at 10.3% for boys and 7.8% for girls, at 24 months. By 24 months, girls had greater FMI (10%) than boys. There were significant differences in FFM (both sexes in all countries) and FM (Brazilian boys, Pakistani and South African girls) by 24 months of age between infants with average, above-average, and below-average HAZ.

CONCLUSION

In a multi-country sample representing more ideal maternal conditions, body composition was heterogeneous even among infants who exhibited ideal length. Having a mean HAZ close to the median of the WHO standard for length reduced FFM between-country heterogeneity but not FM, suggesting that other factors may influence adiposity.

Body composition of infants at 6 months of age using a 3-compartment model

BACKGROUND/OBJECTIVES

Two compartment (2 C) models of body composition, including Air Displacement Plethysmography (ADP) and Deuterium Dilution (DD), assume constant composition of fat-free mass (FFM), while 3-compartment (3 C) model overcomes some of these assumptions; studies are limited in infants. The objective of the present study is to compare 3 C estimates of body composition in 6-mo. old infants from Australia, India, and South Africa, including FFM density and hydration, compare with published literature and to evaluate agreement of body composition estimates from ADP and DD.

METHODS

Body volume and water were measured in 176 healthy infants using ADP and DD. 3C-model estimates of fat mass (FM), FFM and its composition were calculated, compared between countries (age and sex adjusted) and with published literature. Agreement between estimates from ADP and DD were compared by Bland-Altman and correlation analyses.

RESULTS

South African infants had significantly higher % FM (11.5%) and density of FFM compared to Australian infants. Australian infants had significantly higher % FFM (74.7 ± 4.4%) compared to South African infants (71.4 ± 5.0) and higher FFMI (12.7 ± 0.8 kg/m2) compared to South African (12.3 ± 1.2 kg/m2) and Indian infants (11.9 ± 1.0 kg/m2). FFM composition of present study differed significantly from literature. Pooled three country estimates of FM and FFM were comparable between ADP and DD; mean difference of -0.05 (95% CI: -0.64, +0.55) kg and +0.05 (95% CI: -0.55, +0.64) kg.

CONCLUSIONS

3C-model estimates of body composition in infants differed between countries; future studies are needed to confirm these findings and investigate causes for the differences.

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.

Infant body composition at 6 and 24 months: what are the driving factors?

BACKGROUND/OBJECTIVE

Available evidence on infant body composition is limited. This study aimed to investigate factors associated with body composition at 6 and 24 months.

SUBJECTS/METHODS

Multicenter study with data from a 0 to 6-mo cohort (Australia, India and South Africa) and a 3 to 24-mo cohort (Brazil, Pakistan, South Africa, and Sri Lanka). For the 0-6-mo cohort, body composition was assessed by air-displacement plethysmography (ADP) and for the 3-24-month cohort by the deuterium dilution (DD) technique. Fat mass (FM), fat-free mass (FFM), FM index (FMI), and FFM index (FFMI) were calculated. Independent variables comprised the Gini index of the country, maternal and infant characteristics, and breastfeeding pattern at 3 months. For the 3-24-mo cohort, breastfeeding, and minimum dietary diversity (MDD) at 12 months were also included. Crude and adjusted analyses stratified by sex were conducted by multilevel modelling using mixed models.

RESULTS

At 6 months, every 1 kg increase in birth weight was associated with an increase of 0.716 kg in FFM and 0.582 kg/m2 in FFMI in girls, whereas in boys, the increase was of 0.277 kg in FFM. At 24 months, compared to those weaned before 12 months, girls still breastfed at 12 months presented a decrease of 0.225 kg in FM, 0.645 kg in FFM and 0.459 kg/m2 in FFMI, and in boys the decreases were of 0.467 kg in FM, 0.603 kg in FFM and 0.628 kg/m2 in FFMI.

CONCLUSION

Birth weight and breastfeeding are independent predictors of body composition in early life, irrespective of sex.

Correlates of Body Composition in Children with Stunting: A Cross-sectional Study in Uganda

BACKGROUND

Development of body composition (BC) may be disrupted in children with stunting. Such disruption may affect the later risk of excess adiposity and metabolic health, yet few studies have investigated correlates of BC in children with stunting.

OBJECTIVES

We aimed to investigate nutritional status, infection and inflammation, breastfeeding behaviors, and other factors as correlates of BC in children with stunting.

METHODS

Among Ugandan children with a height-for-age z-score <-2, BC was estimated using bioelectrical impedance analysis and compared with United Kingdom references. We used multiple linear regression analysis to identify correlates of fat mass (FM), fat-free mass (FFM), FM-index (FMI), and FFM index (FFMI) and height, adjusting for gender and age.

RESULTS

In 750 children aged 1-5 y, FMI was 0.46 (95% confidence interval [CI]: 0.38, 0.54] and FFMI 0.18 [95% CI: 0.11, 0.26) z-scores lower than United Kingdom references. Elevated serum α1-acid glycoprotein was associated with 1.14 [0.76, 1.52] cm lower height, 0.50 [0.35, 0.65] kg/m2 less FFMI, and 0.48 [0.31, 0.66] kg/m2 greater FMI. Similar, weaker, associations for elevated serum C-reactive protein were detected. A positive malaria rapid test was associated with 0.64 [0.25, 1.02] cm shorter height, but 0.36 [0.18, 0.54] kg/m2 greater FMI. Anemia (according to hemoglobin) was associated with 0.20 [0.07, 0.33] kg less FFM in proportion to shorter height. Longer breastfeeding duration was associated with 0.03 [0.02, 0.04] kg greater FFM per month, in proportion to greater height.

CONCLUSIONS

These children exhibited deficits in FM and FFM, proportionally to their stunted height, compared with United Kingdom references. Systemic inflammation correlated inversely with linear growth and FFM but positively with fatness, making it a possible target for intervention where fat-free tissue accretion is desirable. Longer breastfeeding may offer protection to lean linear growth, but findings for micronutrients were less clear. Longitudinal studies are warranted to support these findings. The study was registered at www.isrctn.com (Ref. ISRCTN13093195).

Expected and Desirable Preterm and Small Infant Growth Patterns

Adequate nutrition is necessary for achieving optimal growth and neurodevelopment. Growth is a natural and expected process that happens concomitantly with rapid advancements in neurodevelopment. Serial weight, length, and head circumference growth measures are essential for monitoring development, although identifying pathological deviations from normal growth can pose challenges. Appropriate growth assessments require considerations that a range of sizes for length, head circumference, and weight are expected and appropriate. Because of genetic differences and morbidities, there is a considerable overlap between the growth of healthy infants and those with growth alterations. Parents tend to be over-concerned about children who plot low on growth charts and often need reassurance. Thus, the use of terms such as "poor" growth or growth "failure" are discouraged when growth is approximately parallel to growth chart curves even if their size is smaller than specific percentiles. No specific percentile should be set as a growth goal; individual variability should be expected. An infant's size at birth is important information that goes beyond the common use of prognostic predictions of appropriate compared with small or large for gestational age. The lower the birthweight, the lower the nutrient stores and the more important the need for nutrition support. Compared to term infants, preterm infants at term-equivalent age have a higher percentage of body fat, but this diminishes over the next months. Current research findings support expert recommendations that preterm infants should grow, after early postnatal weight loss, similar to the fetus and then term-born infants, which translates to growth approximately parallel to growth chart curves. There is no need for a trade-off between optimum cognition and optimum future health. Each high-risk infant needs individualized nutrition and growth assessments. This review aims to examine infant growth expectations and messaging for parents of preterm and term-born infants within the broader causal framework.

Hormonal Determinants of Growth and Weight Gain in the Human Fetus and Preterm Infant

The factors controlling linear growth and weight gain in the human fetus and newborn infant are poorly understood. We review here the changes in linear growth, weight gain, lean body mass, and fat mass during mid- and late gestation and the early postnatal period in the context of changes in the secretion and action of maternal, placental, fetal, and neonatal hormones, growth factors, and adipocytokines. We assess the effects of hormonal determinants on placental nutrient delivery and the impact of preterm delivery on hormone expression and postnatal growth and metabolic function. We then discuss the effects of various maternal disorders and nutritional and pharmacologic interventions on fetal and perinatal hormone and growth factor production, growth, and fat deposition and consider important unresolved questions in the field.