Optimizing Growth and Neurocognitive Development While Minimalizing Metabolic Risk in Preterm Infants

Does Growth Velocity Affect Associations between Birth Weight and Neurodevelopment for Infants Born Very Preterm?

OBJECTIVE

To determine how neonatal growth velocity affects the association between birth weight and neurodevelopmental outcomes in infants born preterm.

STUDY DESIGN

This study is a secondary analysis of the Maternal Omega-3 Supplementation to Reduce Bronchopulmonary Dysplasia in Very Preterm Infants (MOBYDIck) randomized multicenter trial conducted in breastfed infants born at <29 weeks of gestation, whose mothers were supplemented with docosahexaenoic acid or placebo during the neonatal period. Neurodevelopmental outcomes were assessed at 18-22 months of corrected age using the Bayley-III cognitive and language composite scores. The role of neonatal growth velocity was assessed with causal mediation and linear regression models. Subgroup analyses were stratified by birth weight z-score categories (<25th, ≥25th-≤75th, and >75th percentiles).

RESULTS

Neurodevelopmental outcomes were available for 379 children (mean gestational age, 26.7 ± 1.5 weeks). Growth velocity partially mediated the relationships between birth weight and cognitive (β = -1.1; 95% CI, -2.2 to -0.02; P = .05) and language scores (β = -2.1; 95% CI, -3.3 to -0.8; P = .002). An increase by 1 g/kg/day in growth velocity was associated with an increase by 1.1 point in the cognitive score (95% CI, -0.03 to 2.1; P = .06) and 1.9 point in the language score (95% CI, 0.7 to 3.1; P = .001), after adjustment for birth weight z-score. For children with birth weight <25th percentile, a 1 g/kg/day increase in growth velocity was associated with an increase by 3.3 points in the cognitive score (95% CI, 0.5 to 6.0; P = .02) and 4.1 points in the language score (95% CI, 1.3 to 7.0; P = .004).

CONCLUSIONS

Postnatal growth velocity mediated the relationship between birth weight and neurodevelopmental performance, with larger effects for children with lower birth weight.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT02371460.

Preterm infant body composition, working memory, and temperament

Altered body composition in preterm infants is associated with risks to cognitive development, but the effect specific to prefrontal cortex (PFC) development is unknown. We were interested in the impact of fat mass (FM) and fat free mass (FFM) gains out to 4 months corrected gestational age (CGA) on PFC development, as indexed by working memory and temperament. This is a prospective observational pilot study recruiting 100 preterm (<33 weeks gestation), appropriate for gestational age, and very low birth weight infants, of which 49 infants met inclusion criteria. Body composition was measured using air displacement plethysmography at hospital discharge and 4 months CGA. Questionnaire based temperament assessments were completed at 12 and 24 months CGA and a working memory assessment was completed at 24 months CGA. Associations between developmental tests and body composition obtained at term and 4 months were analyzed. Increased FM at discharge was associated with increased fear and decreased soothability at 12 months. Increased FM at 4 months was associated with increased activity level, increased distress from limitations at 12 months and decreased attentional shifting, decreased frustration, and decreased inhibitory control at 24 months. Increased FFM at 4 months was associated with increased activity level at 12 months and increased impulsivity and decreased low intensity pleasure at 24 months. In this exploratory pilot study, increased FM out to 4 months and increased FFM after discharge are associated with negative markers of infant temperament. Infant temperament may be sensitive to body composition status at least to 4 months CGA.

Characterization of D-amino acids in colostral, transitional, and mature preterm human milk

D-Amino acids are regulatory molecules that affect biological processes. Therefore, being able to accurately detect and quantify these compounds is important for understanding their impact on nutrition and health. There is a paucity of information regarding D-amino acids in human milk. We developed a fast method for simultaneous analysis of amino acid enantiomers in human milk using liquid chromatography with tandem mass spectrometry. The method enables the separation of 41 amino acids without chemical derivatization. Our results revealed that human milk from mothers of preterm infants contains concentrations of D-amino acids that range from 0.5 to 45% that of their L-counterparts and that levels of most D-amino acids decrease as the milk production matures. Moreover, we found that Holder pasteurization of milk does not cause racemization of L-amino acids. To our knowledge, this is the first study to describe percentages of D-amino acid levels in human milk; changes in D-amino acid concentration as the milk matures; and the effect of Holder pasteurization on D- and L-amino acid concentrations in human milk.

Variation in Neonatal Nutrition Practice and Implications: A Survey of Australia and New Zealand Neonatal Units

Background: Significant global variation exists in neonatal nutrition practice, including in assigned milk composition values, donor milk usage, fortification regimens, probiotic choice and in methods used to calculate and report nutrition and growth outcomes, making it difficult to synthesize data to inform evidence-based, standardized nutritional care that has potential to improve neonatal outcomes. The Australasian Neonatal Dietitians' Network (ANDiN) conducted a survey to determine the degree to which neonatal nutritional care varies across Australia and New Zealand (A&NZ) and to highlight potential implications.

Materials and Methods: A two-part electronic neonatal nutritional survey was emailed to each ANDiN member (n = 50). Part-One was designed to examine individual dietetic practice; Part-Two examined site-specific nutrition policies and practices. Descriptive statistics were used to examine the distribution of responses.

Results: Survey response rate: 88%. Across 24 NICU sites, maximum fluid targets varied (150–180 mL.kg.d⁻¹); macronutrient composition estimates for mothers' own(MOM) and donor (DM) milk varied (Energy (kcal.dL⁻¹) MOM: 65–72; DM 69–72: Protein (g.dL⁻¹): MOM: 1.0–1.5; DM: 0.8–1.3); pasteurized DM or unpasteurized peer-to-peer DM was not available in all units; milk fortification commenced at different rates and volumes; a range of energy values (kcal.g⁻¹) for protein (3.8–4.0), fat (9.0–10.0), and carbohydrate (3.8–4.0) were used to calculate parenteral and enteral intakes; probiotic choice differed; and at least seven different preterm growth charts were employed to monitor growth.

Discussion: Our survey identifies variation in preterm nutrition practice across A&NZ of sufficient magnitude to impact nutrition interventions and neonatal outcomes. This presents an opportunity to use the unique skillset of neonatal dietitians to standardize practice, reduce uncertainty of neonatal care and improve the quality of neonatal research.

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.

Anthropometry and Body Composition of Preterm Neonates in the Light of Metabolic Programming

The improved survival of preterm infants has led to increased interest regarding their health as adults. In the context of metabolic programming, the connection between perinatal and early postnatal nutrition and growth with health in later life has brought to the fore the role of catch-up growth during the first months of preterm infants' lives and its association with body fat and obesity in childhood or puberty. A state-of-the art review was conducted in order to assess the way catch-up is evaluated, in terms of timing and rate. Adequate growth is of major importance for neurodevelopment; however, it may compete with adiposity or metabolic health. Studies based on body composition assessment have given conflicting results as regards the effect of early versus late and rapid versus slow catch-up growth on later health, mainly attributed to the lack of established criteria and definitions. Given that adequate early nutrition is crucial for the neurodevelopment of preterm infants, further studies are needed on the role of catch-up growth in long-term outcome, using generally accepted qualitative and quantitative criteria.

Concept Analysis of Growth Failure in Preterm Infants in the NICU

Growth failure has not been consistently defined for preterm infants, which contributes to unclear clinical guidelines for optimal growth and development. Therefore, the purpose of this concept analysis was to identify all uses and attributes of the concept, present model and contrary cases, identify antecedents and consequences, define empirical referents, and provide an operational definition of growth failure among preterm infants in the NICU.

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.

Greater Early Gains in Fat-Free Mass, but Not Fat Mass, Are Associated with Improved Neurodevelopment at 1 Year Corrected Age for Prematurity in Very Low Birth Weight Preterm Infants

OBJECTIVE

This work investigates the relationship between early body composition changes and neurodevelopment at 1 year age corrected for prematurity (CA).

STUDY DESIGN

A prospective, longitudinal study to measure body composition weekly in 34 very low birth weight preterm infants using air displacement plethysmography, beginning when infants stabilized after birth until discharge. Neurodevelopmental testing (Bayley Scales of Infant Development-III) was performed at 12 months CA. Linear mixed effects models were used to obtain inpatient subject-specific changes in fat-free mass (FFM) and fat mass (FM), which were then used as predictors of Bayley subscale scores in subsequent linear regression models, adjusting for potential confounders. Protein and energy provision were calculated for the first week of life.

RESULTS

Greater FFM gains while inpatient were associated with improved cognitive and motor scores at 12 months CA (P = .002 for both). These relationships remained significant when adjusting for birth weight, gestational age, and intraventricular hemorrhage (P ≤ .05 for both). Similar analysis was performed for FM gains without significant findings. Increased provision of protein and calories during the first week of life was positively associated with FFM gains (P ≤ .01 for both), but not FM gains (P ≥ .2 for both), throughout hospitalization.

CONCLUSIONS

Increased FFM gains, but not FM gains, during hospitalization are associated with improved neurodevelopment at 12 months CA. As early FM gains may be associated with long-term risk, more research is needed to develop strategies that optimize FFM gains while minimizing FM gains in very low birth weight preterm infants.