A Study to Assess Metabolic Bone Disease of Prematurity Using an Acoustic Method

Inclusion Criteria: * Full term newborns, approximately equal number of male and female newborn, age \<28 days. * Preterm infants, approximately equal number of male and female preterm infants with gestational age at birth \<37 weeks or birth weight \<1500 grams. Exclusion Criteria: * Infants currently requiring continuous cardiovascular medication infusions, including but not limited to, dopamine, epinephrine, milrinone, and dobutamine (may have received these medications in the past. * Infants with major congenital anomalies that may affect bone health or structure. * For full term infants, infants with a history of intrauterine growth restriction or who are small for gestational age (\<10th percentile for weight) at birth.