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New body composition reference charts for preterm infants.

BACKGROUND
The American Academy of Pediatrics (AAP) has recommended that nutritional management of the preterm infant should aim to achieve body composition that replicates the in utero fetus, but intrauterine body composition reference charts for preterm infants are lacking.


OBJECTIVE
Our objective was to create body composition reference curves for preterm infants that approximate the body composition of the in utero fetus from 30 to 36 wk of gestation.


DESIGN
A total of 223 ethnically diverse infants born at 30 + 0 to 36 + 6 wk of gestation were enrolled. Inclusion and exclusion criteria were specified so that the sample would represent healthy appropriately growing fetuses (e.g., singleton, birth weight appropriate for their gestational age, and medically stable). Cross-sectional reference values were generated for fat mass (FM), fat-free mass (FFM), and percentage body fat (PBF) by gestational age (GA), with the use of air-displacement plethysmography (ADP) and the lambda-mu-sigma method for percentile estimation.


RESULTS
GA-specific percentile values and a percentile and z score calculator for FFM, FM, and PBF are presented. These values aligned closely with ADP centile values published for term infants from 36 to 38 wk of gestation. The medians were also similar to the mean values for the reference fetus derived from chemical analysis previously.


CONCLUSIONS
To our knowledge, these are the first body composition reference charts for total FM and FFM at birth in preterm infants to assist in following AAP guidelines. Future work will test the clinical utility of body composition monitoring for improving nutritional management in this population. This trial was registered at clinicaltrials.gov as NCT02855814.