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

Reduced adipose tissue in growth-restricted fetuses using quantitative analysis of magnetic resonance images

OBJECTIVES

Fat-water MRI can be used to quantify tissues' lipid content. We aimed to quantify fetal third trimester normal whole-body subcutaneous lipid deposition and explore differences between appropriate for gestational age (AGA), fetal growth restriction (FGR), and small for gestational age fetuses (SGAs).

METHODS

We prospectively recruited women with FGR and SGA-complicated pregnancies and retrospectively recruited the AGA cohort (sonographic estimated fetal weight [EFW] ≥ 10th centile). FGR was defined using the accepted Delphi criteria, and fetuses with an EFW < 10th centile that did not meet the Delphi criteria were defined as SGA. Fat-water and anatomical images were acquired in 3 T MRI scanners. The entire fetal subcutaneous fat was semi-automatically segmented. Three adiposity parameters were calculated: fat signal fraction (FSF) and two novel parameters, i.e., fat-to-body volume ratio (FBVR) and estimated total lipid content (ETLC = FSF*FBVR). Normal lipid deposition with gestation and differences between groups were assessed.

RESULTS

Thirty-seven AGA, 18 FGR, and 9 SGA pregnancies were included. All three adiposity parameters increased between 30 and 39 weeks (p < 0.001). All three adiposity parameters were significantly lower in FGR compared with AGA (p ≤ 0.001). Only ETLC and FSF were significantly lower in SGA compared with AGA using regression analysis (p = 0.018-0.036, respectively). Compared with SGA, FGR had a significantly lower FBVR (p = 0.011) with no significant differences in FSF and ETLC (p ≥ 0.053).

CONCLUSIONS

Whole-body subcutaneous lipid accretion increased throughout the third trimester. Reduced lipid deposition is predominant in FGR and may be used to differentiate FGR from SGA, assess FGR severity, and study other malnourishment pathologies.

CLINICAL RELEVANCE STATEMENT

Fetuses with growth restriction have reduced lipid deposition than appropriately developing fetuses measured using MRI. Reduced fat accretion is linked with worse outcomes and may be used for growth restriction risk stratification.

KEY POINTS

• Fat-water MRI can be used to assess the fetal nutritional status quantitatively. • Lipid deposition increased throughout the third trimester in AGA fetuses. • FGR and SGA have reduced lipid deposition compared with AGA fetuses, more predominant in FGR.

Effects of Intrauterine Growth Restriction (IUGR) on Growth and Body Composition Compared to Constitutionally Small Infants

(1) Intrauterine growth restriction (IUGR) is associated with multiple morbidities including growth restriction and impaired neurodevelopment. Small for gestational age (SGA) is defined as a birth weight <10th percentile, regardless of the etiology. The term is commonly used as a proxy for IUGR, but it may represent a healthy constitutionally small infant. Differentiating between IUGR and constitutionally small infants is essential for the nutritional management. (2) Infants born at <37 weeks of gestation between 2017 and 2022, who underwent body composition measurement (FFM: fat-free mass; FM: fat mass) at term-equivalent age, were included in this study. Infants with IUGR and constitutionally small infants (SGA) were compared to infants appropriate for gestational age (AGA). (3) A total of 300 infants (AGA: n = 249; IUGR: n = 40; SGA: n = 11) were analyzed. FFM (p < 0.001) and weight growth velocity (p = 0.022) were significantly lower in IUGR compared to AGA infants, but equal in SGA and AGA infants. FM was not significantly different between all groups. (4) The FFM Z-score was significantly lower in IUGR compared to AGA infants (p = 0.017). Being born constitutionally small compared to AGA had no impact on growth and body composition. These data showed that early aggressive nutritional management is essential in IUGR infants to avoid impaired growth and loss of FFM.

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.

Differences in body composition and growth persist postnatally in fetuses diagnosed with severe compared to mild fetal growth restriction

BACKGROUND

Fetal growth restriction (FGR) is most commonly diagnosed in pregnancy if the estimated fetal weight (EFW) is <  10th%. Those with abnormal Doppler velocimetry, indicating placental insufficiency and pathological FGR, demonstrate reduced fat and lean mass compared to both normally growing fetuses and FGR fetuses with normal Dopplers. The aim of this study was to determine how severity of FGR and abnormal Doppler velocimetry impacts neonatal body composition. Among a cohort of fetuses with an EFW <  10th%, we hypothesized that those with abnormal Dopplers and/or EFW <  3rd% would have persistent reductions in lean body mass and fat mass extending into the neonatal period compared to fetuses not meeting those criteria.

METHODS

A prospective cohort of FGR fetuses with an estimated fetal weight (EFW) <  10th% was categorized as severe (EFW <  3rd% and/or abnormal Dopplers; FGR-S) versus mild (EFW 3-10th% ; FGR-M). Air Displacement Plethysmography and anthropometrics were performed at birth and/or within the first 6-8 weeks of life.

RESULTS

FGR-S versus FGR-M were born one week earlier (P = 0.0024), were shorter (P = 0.0033), lighter (P = 0.0001) with smaller weight-for-age Z-scores (P = 0.0004), had smaller head circumference (P = 0.0004) and lower fat mass (P = 0.01) at birth. At approximately 6-8 weeks postmenstrual age, weight, head circumference, and fat mass were similar but FGR-S neonates were shorter (P = 0.0049) with lower lean mass (P = 0.0258).

CONCLUSION

Doppler velocimetry abnormalities in fetuses with an EFW <  10th% identified neonates who were smaller at birth and demonstrated catch-up growth by 6-8 weeks of life that favored fat mass accretion over lean mass and linear growth.

Body Composition of Infants Born with Intrauterine Growth Restriction: A Systematic Review and Meta-Analysis

Intrauterine growth restriction (IUGR) may predispose metabolic diseases in later life. Changes in fat-free mass (FFM) and fat mass (FM) may explain this metabolic risk. This review studied the effect of IUGR on body composition in early infancy. Five databases and included studies from all countries published from 2000 until August 2021 were searched. Participants were IUGR or small-for-gestational age (SGA) infants, and the primary outcomes were FFM and FM. Eighteen studies met the inclusion criteria, of which seven were included in the meta-analysis of primary outcomes. Overall, intrauterine growth-restricted and SGA infants were lighter and shorter than normal intrauterine growth and appropriate-for-gestational age infants, respectively, from birth to the latest follow up. They had lower FFM [mean difference −429.19 (p = 0.02)] and FM [mean difference −282.9 (p < 0.001)]. The issue of whether lower FFM and FM as reasons for future metabolic risk in IUGR infants is intriguing which could be explored in further research with longer follow-up. This review, the first of its kind can be useful for developing nutrition targeted interventions for IUGR infants in future.

Body Composition of Preterm Infants following Rapid Transition to Enteral Feeding

OBJECTIVE

This study aimed to evaluate body composition at the time of hospital discharge in very preterm infants following rapid transition to full enteral feeding.

STUDY DESIGN

We conducted a prospective, observational, cross-sectional study and included 105 preterm infants <32 gestational age or birth weight <1,500 g, born between April 2015 and December 2020, following rapid transition to full enteral feeding (≥140 mL/kg/day). Fat mass/total body mass (BF%) and fat-free mass (FFM) were measured at the time of hospital discharge using air displacement plethysmography.

RESULTS

Median and interquartile range (Q1-Q3) of gestational age at birth (GA) was 27.3 (26.1-28.7) weeks and birth weight 845 (687-990) g. Time to reach full enteral feeding was 5 (5-7) days. At 37.6 weeks (36.1-39.0) postmenstrual age (PMA), BF% was 17.0% (14.9-19.8) and FFM 2,161 g (1,966-2,432). BF% was not associated with GA, and not different between small and appropriate for gestational age infants. FFM was significantly lower in infants born small for gestational age.

CONCLUSIONS

Following rapid transition to full enteral feeding, FFM and BF% at discharge were similar to other preterm populations. BF% and FFM were not associated with GA at birth but with PMA at measurement. FFM was lower and BF% higher compared to term infants at birth, suggesting diminished parenchymal growth in preterm infants. Continued monitoring of body composition, metabolic health, and neurological development is needed to study long-term effects.

MACRONUTRIENTS OF MOTHERS' MILK OF VERY LOW BIRTH WEIGHT INFANTS: ANALYSIS ACCORDING TO GESTATIONAL AGE AND MATERNAL VARIABLES

Objective:

To analyze the composition of macronutrients present in the milk of mothers of preterm newborn infants (PTNB) - protein, fat, carbohydrate, and calories - by gestational age (GA), chronological age (CA) and maternal variables.

Methods:

Longitudinal study that analyzed 215 milk samples from the 51 mothers of PTNB admitted in three Neonatal Intensive Care Units of Rio de Janeiro from May/2013-January/2014. Milk collection was performed by pickup pump, on a fixed day of each week until discharge. The spectrophotometric technique with Infrared Analysis (MilkoScan Minor 104) was used for the quantitative analysis. A sample of 7 mL of human milk was taken from the total volume of milk extracted by the mother. The data was grouped by GA (25-27, 28-31, 32-36, 37-40 weeks) and by CA (zero to 4, 5-8, 9-12, 13-16 weeks).

Results:

Protein, carbohydrate, fat and calories did not show any pattern of change, with no difference among groups of GA. When the macronutrients were analyzed by groups of CA, protein decreased, with significant difference between the first two groups of CA. Carbohydrates, fat and calories presented increasing values in all groups, without significant differences. Weight gain during pregnancy, maternal hypertension and maternal age were associated with changes in fat and calories in the first moment of the analysis of milk.

Conclusions:

There was a significant decrease in the levels of protein during the first eight weeks after birth. CA may be an important factor in the composition of human milk.