The American Academy of Pediatrics has recommended that growth in size (weight, length, and head circumference) and in body composition (fat and lean mass) in preterm infants should adhere as close as possible to the growth and body composition of a healthy infant in utero at the same gestational age. However, there are no body composition reference curves available at this time for the preterm infant population. The purpose of this study is to collect cross-sectional body composition data using air displacement plethysmography (PEA POD Infant Body Composition System, Life Measurement, Inc) on approximately 240 preterm infants within 3 days of birth, for the purpose of generating means, standard deviations, and percentile values for total body fat mass, total fat free mass, and percent body fat for infants born at 30-36 weeks gestation. Relatively healthy infants without evidence of growth retardation will be selected for form the reference sample. The goal is to generate a set of common reference curves to be used in clinical centers against which to compare body composition status for individual infants.

Inclusion Criteria:

• Appropriate for gestational age (AGA), singleton, 30+0 and 36+6 weeks gestational age

Exclusion Criteria:

• Congenital defects that affect growth
• Inability to tolerate room air for 5 minutes without desaturation or bradycardia
• <1 kg birth weight
• Parents did not provide consent

AGA, singleton, healthy infants born between 30+0 and 36+6 weeks gestation were eligible. The study was conducted between 2010 and 2015 at three tertiary NICU's in the United States: the University of Minnesota Masonic Children's Hospital in Minneapolis, MN (referred to hereafter as the MN site), Santa Clara Valley Medical Center in San Jose, CA (referred to as the SC site), and Baystate Medical Center in Springfield, MA (referred to as BS).