Differences in body composition and resting energy expenditure in childhood in preterm children born with very low birth weight

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.

Small for gestational age preterm infants and later adiposity and height: A systematic review and meta-analysis

BACKGROUND

Overweight and obesity and their consequent morbidities are important worldwide health problems. Some research suggests excess adiposity origins may begin in fetal life, but unknown is whether this applies to infants born preterm.

OBJECTIVE

The objective of the study was to assess the association between small for gestational age (SGA) birth and later adiposity and height among those born preterm.

DATA SOURCES

MEDLINE, EMBASE and CINAHL until October 2022.

STUDY SELECTION AND DATA EXTRACTION

Studies were included if they reported anthropometric (adiposity measures and height) outcomes for participants born preterm with SGA versus non-SGA. Screening, data extraction and risks of bias assessments were conducted in duplicate by two reviewers.

SYNTHESIS

We meta-analysed across studies using random-effects models and explored potential heterogeneity sources.

RESULTS

Thirty-nine studies met the inclusion criteria. In later life, preterm SGA infants had a lower body mass index (-0.66 kg/m2 , 95% CI -0.79, -0.53; 32 studies, I2  = 16.7, n = 30,346), waist circumference (-1.20 cm, 95% CI -2.17, -0.23; 13 studies, I2  = 19.4, n = 2061), lean mass (-2.62 kg, 95% CI -3.45, 1.80; 7 studies, I2  = 0, n = 205) and height (-3.85 cm, 95% CI -4.73, -2.96; 26 studies, I2  = 52.6, n = 4174) compared with those preterm infants born non-SGA. There were no differences between preterm SGA and preterm non-SGA groups in waist/hip ratio, body fat, body fat per cent, truncal fat per cent, fat mass index or lean mass index, although power was limited for some analyses. Studies were rated at high risk of bias due to potential residual confounding and low risk of bias in other domains.

CONCLUSIONS

Compared to their preterm non-SGA peers, preterm infants born SGA have lower BMI, waist circumference, lean body mass and height in later life. No differences in adiposity were observed between SGA preterm infants and non-SGA preterm infants.

Bone density and body composition in small for gestational age children with adequate catch up growth: A preliminary retrospective case control study

BACKGROUND

Fetal growth patterns and birth weight (BW) have been associated with bone mineral density (BMD) and content (BMC) throughout infancy and childhood up to early adulthood. We hypothesized that in small for gestational age (SGA) children, compensatory infant catch-up growth to normal height centiles counteracts the adverse consequences of low BW on bone accrual.

AIM

To evaluate BMD and BMC of SGA children born at term who experienced a normal catch-up growth as compared to children born appropriate for gestational age (AGA).

PATIENTS

We recruited 53 SGA (26 females) and 60 AGA children (27 females), aged 6 to 18 years, matched for sex and body mass index (BMI). Fat mass (FM); Free fat mass (FFM); Lumbar spine and Total body less head (TBLH) BMD; BMC and BMD standard deviation scores corrected for body size (BMAD, BMAD z-score and TBLH BMD/Height) and TBLH BMC for FFM (TBLHBMC/FFM) were derived from Dual Energy X-ray absorptiometry (DXA) scans.

RESULTS

SGA and AGA children did not differ in any auxological, body composition and bone parameters appropriately adjusted for height and FFM. BMI, FM and, remarkably, FFM were significantly correlated with bone mass parameters in both groups while no correlation was found between FM and FFM with the BW SDS in the univariate analysis.

CONCLUSION

Our preliminary data demonstrate that SGA children born at term who recover from their growth deficiency through catch-up growth achieve bone mass and body composition not different from children born AGA.

Catch-Up Growth in Children Born Small for Gestational Age Related to Body Composition and Metabolic Risk at Six Years of Age in the UK

OBJECTIVES

To determine differences in body composition and glucose metabolism according to childhood growth outcomes in a population-based sample of children born small for gestational age (SGA).

METHODS

A single-centre study of 259 children born SGA identified through hospital records and contacted when aged 4-7 years. Questionnaire data on pre/perinatal history and growth parameters during childhood was collected from the parents, and in a subgroup of 150 children face-to-face assessments were performed, including anthropometric parameters, lean and fat mass, blood pressure, fasting glucose, and C-peptide.

RESULTS

Based on the questionnaires, few children had formal clinic follow-up of growth, but 7% of the cohort showed a height and weight of <-2SDS during childhood, and only 2 children met the criteria for growth hormone therapy. Out of the 150 children assessed at a mean age of 6.1 ± 0.8 years, 122 (81%) showed a catch-up growth in weight. Compared to those without weight catch-up, these children had a higher fat mass index (3.13 ± 1.36 vs. 2.56 ± 0.91 kg/m2, p = 0.04), trunk-to-limb fat mass ratio (0.63 ± 0.14 vs. 0.56 ± 0.08, p = 0.002), systolic blood pressure SDS (0.09 ± 0.71 vs. -0.32 ± 0.63, p = 0.008), fasting glucose (4.5 ± 0.5 vs. 4.3 ± 0.5 mmol/L, p = 0.03), and C-peptide (306 ± 116 vs. 256 ± 112 pmol/L, p = 0.08). Among children with weight catch-up growth, those with less height gain had a lower limb lean mass index (4.25 ± 0.48 vs. 4.48 ± 0.56 kg/m2, p = 0.02) and fat mass index (1.57 ± 0.59 vs. 1.83 ± 0.77 kg/m2, p = 0.04).

CONCLUSIONS

Within this population-based sample of SGA children, catch-up growth in weight was associated with higher abdominal fat mass, blood pressure and glycemia; furthermore, in these children, less height gain was associated with reduced limb lean and fat mass.

A systematic review indicates an association between birth weight and body fat in childhood

AIM

To summarise the existing evidence regarding the body fat of small or large for gestation subjects, evaluated from birth up to 18 years of age.

METHODS

The PRISMA guidelines were adopted for the current systematic review, including studies having evaluated body fat with bioelectrical impedance analysis, air displacement plethysmography, dual-energy X-ray absorptiometry or magnetic resonance imaging.

RESULTS

A total of 31 studies was included. The balance of evidence suggests that small for gestation infants have decreased fat mass at birth; postnatally they experience increased adiposity. In the long term, however, the evidence is inconclusive, since some studies suggest that foetal-restricted children with increased catch-up growth are at increased risk of fat accumulation, whereas other studies suggest a neutral or even negative association. Large for gestation infants have increased fat mass at birth, but in the long term, they have a lower body fat ratio, especially when they develop a catch-down growth.

CONCLUSION

Some studies suggested that foetal-restricted children with increased catch-up growth are at increased risk of later adiposity, while other studies suggested a neutral or negative association. Given that the evidence is inconclusive, further studies are warranted. Large for gestation subjects have lower body fat when they develop catch-down growth.

Lower insulin sensitivity remains a feature of children born very preterm

BACKGROUND

The first report of children born very preterm (<32 weeks of gestation) having insulin resistance was made 16 years ago. However, neonatal care has improved since. Thus, we aimed to assess whether children born very preterm still have lower insulin sensitivity than term controls.

METHODS

Participants were prepubertal children aged 5 to 11 years born very preterm (<32 weeks of gestation; n = 51; 61% boys) or at term (37-41 weeks; n = 50; 62% boys). Frequently sampled intravenous glucose tolerance tests were performed, and insulin sensitivity was calculated using Bergman's minimal model. Additional clinical assessments included anthropometry, body composition using whole-body dual-energy X-ray absorptiometry scans, clinic blood pressure, and 24-hour ambulatory blood pressure monitoring.

RESULTS

Children born very preterm were 0.69 standard deviation score (SDS) lighter (P < .001), 0.53 SDS shorter (P = .003), and had body mass index 0.57 SDS lower (P = .003) than children born at term. Notably, children born very preterm had insulin sensitivity that was 25% lower than term controls (9.4 vs 12.6 × 10^-4 minutes^-1 ·[mU/L]; P = .001). Other parameters of glucose metabolism, including fasting insulin levels, were similar in the two groups. The awake systolic blood pressure (from 24-hour monitoring) tended to be 3.1 mm Hg higher on average in children born very preterm (P = .054), while the clinic systolic blood pressure was 5.4 mm Hg higher (P = .002).

CONCLUSIONS

Lower insulin sensitivity remains a feature of children born very preterm, despite improvements in neonatal intensive care. As reported in our original study, our findings suggest the defect in insulin action in prepubertal children born very pretermis primarily peripheral and not hepatic.

EFFECTS OF HAMMOCK POSITIONING ON CLINICAL PARAMETERS IN PRETERM INFANTS ADMITTED TO A NEONATAL INTENSIVE CARE UNIT: A SYSTEMATIC REVIEW

Objective:

To review the effects of the hammock positioning on clinical parameters of preterm newborn infants (PTNB) admitted to the Neonatal Intensive Care Unit (NICU).

Data sources:

This was a systematic review performed by searching the Pubmed, Lilacs, SciELO and PEDro databases. Intervention studies in English, Portuguese and Spanish that evaluated the effects of hammock positioning on clinical parameters of PTNB admitted to the NICU were selected. Three search strategies were used: 1) hammock positioning OR patient positioning AND intensive care units AND infant, newborn; 2) hammock positioning OR patient positioning AND intensive care units; 3) hammock positioning OR patient positioning AND intensive care units, neonatal. There was no restriction on the year of publication of the articles. Methodological quality was assessed by the PEDro scale.

Data synthesis:

Among 597 articles, only six were included and 139 neonates with gestational ages between 26 and 37 weeks and an average gestational weight <2240g were analyzed. Four studies included patients without any associated pathology and most of them placed the PTNB supine in hammock positioning. The duration of the intervention ranged from 15 to 180 minutes and most applied it at just one moment. There was an improvement in heart rate (HR), respiratory rate (RR) and pain (3/4 studies), as well as gains in peripheral oxygen saturation (SpO2) (2/4 studies). Only one study reported worsening of SpO2 with the intervention. The methodological quality of the studies was classified as low.

Conclusions:

Although this review suggests improvement with hammock positioning in HR, RR and pain in PTNB, the low methodological quality makes the results inconsistent.

Developmental Programming of Body Composition: Update on Evidence and Mechanisms

PURPOSE OF REVIEW

A growing body of epidemiological and experimental data indicate that nutritional or environmental stressors during early development can induce long-term adaptations that increase risk of obesity, diabetes, cardiovascular disease, and other chronic conditions-a phenomenon termed "developmental programming." A common phenotype in humans and animal models is altered body composition, with reduced muscle and bone mass, and increased fat mass. In this review, we summarize the recent literature linking prenatal factors to future body composition and explore contributing mechanisms.

RECENT FINDINGS

Many prenatal exposures, including intrauterine growth restriction, extremes of birth weight, maternal obesity, and maternal diabetes, are associated with increased fat mass, reduced muscle mass, and decreased bone density, with effects reported throughout infancy and childhood, and persisting into middle age. Mechanisms and mediators include maternal diet, breastmilk composition, metabolites, appetite regulation, genetic and epigenetic influences, stem cell commitment and function, and mitochondrial metabolism. Differences in body composition are a common phenotype following disruptions to the prenatal environment, and may contribute to developmental programming of obesity and diabetes risk.

Premature small for gestational age infants fed an exclusive human milk-based diet achieve catch-up growth without metabolic consequences at 2 years of age

OBJECTIVE

To compare postdischarge growth, adiposity and metabolic outcomes of appropriate for gestational age (AGA) versus small for gestational age (SGA) premature infants fed an exclusive human milk (HM)-based diet in the neonatal intensive care unit.

DESIGN

Premature infants (birth weight ≤1250 g) fed an exclusive HM-based diet were examined at 12-15 months corrected gestational age (CGA) (visit 1) for anthropometrics, serum glucose and non-fasting insulin, and at 18-22 months CGA (visit 2) for body composition by dual-energy X-ray absorptiometry.

RESULTS

Of 51 children, 33 were AGA and 18 were SGA at birth. The SGA group had weight gain (g/day) equal to AGA group during the follow-up period. SGA had a significantly greater body mass index (BMI) z-score gain from visit 1 to visit 2 (0.25±1.10 vs -0.21±0.84, p=0.02) reflecting catch-up growth. There were no significant differences in total fat mass (FM) and trunk FM between groups. SGA had significantly lower insulin level (5.0±3.7 vs 17.3±15.1 µU/mL, p=0.02) and homeostatic model of assessment-insulin resistance (1.1±0.9 vs 4.3±4.1, p=0.02). Although regional trunk FM correlated with insulin levels in SGA (r=0.893, p=0.04), they had lower insulin level compared with AGA and no difference in adiposity.

CONCLUSIONS

SGA premature infants who received an exclusive HM-based diet exhibited greater catch-up growth without increased adiposity or elevated insulin resistance compared with AGA at 2 years of age. An exclusive HM-based diet may improve long-term body composition and metabolic outcomes of premature infants with ≤1250 g birth weight, specifically SGA.

A low resting metabolic rate in late childhood is associated with weight gain in adolescence

BACKGROUND AND OBJECTIVES

Lower total energy expenditure (TEE) and resting metabolic rate (RMR) are associated with greater weight gain in Native American adults. Whether these effects exist in childhood is unclear. We hypothesized that lower energy expenditure measured in childhood would predict greater relative change in body mass index (BMI) during adolescence.

METHODS

Measurements of height, weight, body composition, RMR and TEE were completed in 181 Native American children at exams done at age 5 and 10years, with 126 children having biennial follow-up assessments of weight and height after age 10years until age 20years. TEE and RMR were adjusted for age, sex, height, fat mass and fat free mass. BMI-change was assessed using population specific and Center for Disease Control (CDC) BMI z-scores and change in the relative difference to the 95th BMI-centile.

RESULTS

Lower adjusted RMR at age 10years was associated with greater increase in population-specific and CDC BMI z-scores, greater increase in the relative difference to the 95th BMI-centile and greater weight gain (all r≤-0.22, p≤0.01). However, no association was found with adjusted RMR at age 5years and with adjusted TEE and physical activity level assessed at age 5 or 10years.

CONCLUSIONS

Lower adjusted RMR at age 10years predicted greater change in adolescent BMI z-score indicating that the effects of relatively low metabolic rate on future weight gain in this population may begin in late childhood.

Energy expenditure, growth, and nutritional therapy in appropriate and small for gestational age preterm infants

OBJECTIVE

To evaluate the resting energy expenditure, growth, and quantity of energy and macronutrients intake in a group of preterm newborns.

METHODS

The cohort study was performed with appropriate and small for gestational age preterm infants (birth weight lower than 1500g or gestational age<32 weeks). Resting energy expenditure was measured using indirect calorimetry on the 7th, 14th, 21st, and 28th days of life, and at discharge. Length, head circumference and body weight were assessed weekly. Nutritional therapy was calculated during the hospital stay and the information for each type of food was recorded in software that calculates the total amount of energy and macronutrients.

RESULTS

61 preterm infants were followed; 43 appropriate and 18 small for gestational age infants. There was no statistical difference for resting energy expenditure between the groups, and it increased from the first to the fourth week of life (appropriate: 26.3% and small: 21.8%). Energy intake in the first two weeks of life was well below the energy requirement.

CONCLUSION

Considering that the results demonstrate high energy expenditure during the first weeks of life, there is an evident need to provide the best quality of nutrition for each child in the first weeks of life so that preterm infants with or without intrauterine growth restriction can achieve their maximum potential for growth and development.

Patterns of Infancy Growth and Metabolic Hormonal Profile Are Different in Very-Low-Birth-Weight Preterm Infants Born Small for Gestational Age Compared to Those Born Appropriate for Gestational Age

BACKGROUND/AIMS

An increased preterm birth survival rate is associated with long-term neurological and metabolic risks; thus, our aim was to evaluate whether early patterns of infancy anthropometry and metabolic hormonal profile differ in preterm infants born small for gestational age (SGA) or appropriate for gestational age (AGA) from birth to 36 months of corrected age (CA).

METHODS

We recruited 110 very-low-birth-weight (VLBW) preterm infants (AGA = 60 and SGA = 50) with a mean birth weight of -2.39 ± 0.77 versus 0.57 ± 0.54 standard deviation scores (SDS) (p < 0.01) and birth length of -2.1 ± 1.05 versus -0.44 ± 0.82 SDS (p < 0.01), respectively. Anthropometry and blood sampling for insulin, insulin-like growth factor (IGF)-II, IGF-I, and leptin were performed for up to 3 years.

RESULTS

All neonates increased their weight, length, and head circumference SDS during the early inpatient period. Up to 90% reached a normal length within this period. The IGF-II, insulin, and glycemia concentrations changed in parallel with weight. In the first year of CA, only SGA infants gained weight and height SDS. The homoeostatic model assessment had a trend toward higher values in SGA infants at 24 and 36 months (p = 0.06 and p = 0.07).

CONCLUSION

Being SGA is the strongest predictor of early recovery of height in VLBW preterm infants. Follow-up will allow us to determine whether the differences in the growth patterns of VLBW preterm infants by birth weight SDS persist.

The impact of intrauterine and extrauterine weight gain in premature infants on later body composition

BackgroundThe impact of intrauterine and extrauterine growth on later insulin resistance and fat mass (FM) in very low birth weight (VLBW) infants is not well established. The aim of our study was to evaluate the effects of intrauterine and early/late extrauterine growth on later insulin resistance and body composition in VLBW infants from 6 months' corrected age (CA) to 36 months.MethodsProspective measurements of body composition by dual-energy X-ray absorptiometry and insulin resistance by homeostasis model assessment insulin resistance (HOMA-IR) along with other fasting plasma biochemistries were made in 95 VLBW infants at 6, 12, 18, and 24 months' CA and 36 months' postnatal age. Mixed-effect models were used to evaluate the effects of age, sex, maturation status, and Δweight SD score on percentage FM (PFM), FM index (FMI), fat-free mass index (FFMI), and HOMA-IR.ResultsPFM and FMI were negatively associated with a decrease in weight-SD scores from birth to 36 weeks' postmenstrual age (PMA; P=0.001) and from 36 weeks' PMA to 6 months' CA (P=0.003). PFM and FMI were higher in AGA than in small for gestational age (SGA) infants. HOMA-IR was not associated with the Δweight-SD scores in either period.ConclusionsCatch-down growth in terms of weight is associated with persistently lower adiposity but not insulin resistance up to 36 months of age.

Body Composition within the First 3 Months: Optimized Correction for Length and Correlation with BMI at 2 Years

BACKGROUND/AIMS

Although early infant growth has implications for future health, body composition reference data in infancy are limited. The aim of this study was to describe reference data for fat mass (FM) and fat-free mass (FFM) corrected for length (L) within the first 3 months and to evaluate if these measures predict the body mass index (BMI) at 2 years.

METHODS

Term infants had air displacement plethysmography performed at birth (n = 1,063) and approximately 2 months later (n = 922, between 49 and 86 days). Age- and sex-specific reference data were generated for FM, FFM, FM/L³ and FFM/L² and compared with BMI at 2 years.

RESULTS

FM/L³ and FFM/L² were the optimal indices independent of length. In the first 3 months, mean FM/L³ increased (males, from 2.7 to 5.9 kg/m³; females, from 3.2 to 6.1 kg/m³), whereas FFM/L² remained relatively stable (males, from 11.8 to 12.7 kg/m²; females, from 12.8 to 12.1 kg/m²). The odds of a BMI Z-score ≥2 at 2 years increased with increasing FM (OR 2.7, 95% CI 1.97-3.7) and weight (OR 2.27, 95% CI 1.64-3.13) Z-scores at 2 months.

CONCLUSIONS

FM/L³ and FFM/L² provide length-independent measures of FM and FFM in infancy. During the first 3 months, there is an increase in FM/L³, but not in FFM/L². The weight Z-score at 2 months is as good at predicting BMI at 2 years as body composition parameters. © 2016 S. Karger AG, Basel.

Long-term metabolic risk among children born premature or small for gestational age

Accumulating evidence suggests that both the intrauterine environment and growth during early life can influence the development of chronic noncommunicable diseases, such as type 2 diabetes mellitus and cardiovascular disease, in adulthood. Here, we review the available human data supporting increased metabolic risk among children born premature or small for gestational age; the adrenal and pubertal modifications that contribute to this risk; metabolic changes that occur during adolescence and early adulthood; and approaches to potentially modify or decrease risk of metabolic disease. The risks associated with delivery at term or preterm are compared for each period of life. Knowledge of these associations is fundamental for the paediatric community to develop preventive strategies early during postnatal life.

[Body composition and metabolic risk in small for gestational age children treated with growth hormone]

BACKGROUND AND OBJECTIVES

Small for gestational age (SGA) children are at increased risk of metabolic syndrome. Our objective is to evaluate changes in body composition produced by growth hormone (GH) treatment.

PATIENTS AND METHOD

A group of 28 SGA children without catch-up growth and undergoing treatment with GH was selected for evaluation. Over the course of 3 years from the beginning of the treatment with GH, the children's body composition variables (bone mineral density [BMD], fat and lean body mass proportion) were evaluated annually with dual-energy X-ray absorptiometry. A study of correlation between metabolic and body composition variables was also made.

RESULTS

Treatment with GH produces a reduction in fat mass proportion in relation to lean body mass, decreasing from 25.94±6.09 to 22.88±5.38% (P=.034). In the abdominal regions we observe an increase in lean mass, from 1,356,91±426,71 to 2,570,96±814,36g (P=.000) and a tendency for visceral fat deposits to decrease. BMD in lumbar vertebrae improved from -1.55±0.68 to -0.90±0.79Z (P=.019).

CONCLUSIONS

Treatment with GH produces changes in body composition, improving BMD and increasing the proportion of lean body mass with a reduction in fat mass. If these changes persisted into adulthood, they may cause a reduction in the metabolic and cardiovascular risk in this group of patients.

Relationship between fat mass measured by dual-energy X-ray absorptiometry and leptin in preterm infants between term age and 6 months' corrected age

BACKGROUND/AIMS

In term subjects, fat mass (FM) is positively associated with leptin, whereas studies in preterm infants show conflicting results. However, none of these studies measured FM by dual-energy X-ray absorptiometry (DEXA). This study aims to relate FM measured by DEXA in relation to leptin and growth in preterm infants.

METHODS

In 139 preterm infants, weight (kg) and length (cm) were measured at birth, term age, and 6 months' corrected age (CA). FM (kg), measured by whole-body DEXA, and leptin (µg/l) were measured at term age and 6 months' CA.

RESULTS

At term age and 6 months' CA, FM was associated with leptin (β = 1.94, 95% CI: 1.51-2.36, and β = 0.37, 95% CI: 0.26-0.48, respectively; p < 0.001). Gain in weight standard deviation score (SDS) between term age and 6 months' CA was associated with FM and leptin at 6 months' CA (β = 0.24, 95% CI: 0.18-0.30, and β = 0.25, 95% CI: 0.16-0.33, respectively; p < 0.001).

CONCLUSION

In preterm infants, FM measured by DEXA is associated with leptin, which indicates that leptin is a marker of body FM during the first 6 months after term age. Gain in weight SDS between term age and 6 months' CA results in higher FM and higher leptin at 6 months' CA.

Boys who are born preterm show a relative lack of fat-free mass at 5 years of age compared to their peers

AIM

Prematurity is associated with features of metabolic syndrome in young adulthood. We investigated the body composition and blood pressure of children born preterm.

METHODS

A longitudinal, observational study was conducted with preterm infants who had a birth weight of <1500 g and a gestational age of <32 weeks. Growth and body composition were assessed by air displacement plethysmography at term equivalent age and at school age and were compared to those of 61 healthy, term breastfed subjects.

RESULTS

A total of 63 preterm infants were enrolled. At term equivalent age, growth and fat-free mass were lower in preterm infants than in term newborns, but fat mass was higher. At 5 years of age, children born preterm were still lighter and shorter than children born at term. When the results were analysed by gender, the fat-free mass index was lower in boys born preterm than in their peers (12.1 ± 1.1 versus 13.0 ± 1.0 kg/h(2) p < 0.005), whereas no difference was detected among girls. Diastolic blood pressure was higher in children born preterm than in children born at term (61.14 ± 7.8 vs 56.69 ± 8.2 mmHg, p = 0.009).

CONCLUSION

Boys born preterm showed a relative lack of fat-free mass at school age compared to their peers.