The objective of the project is to identify clinical factors (nutritional and non-nutritional) which are associated with ultrasound measurements of muscle and adipose tissue and to determine whether these ultrasound measurements are predictive of later metabolic and neurodevelopmental outcomes in premature infants, a population at risk for developmental delay, obesity, and metabolic disease. The investigators expect that a better understanding of these relationships will lead to the incorporation of ultrasound into routine nutritional management of preterm infants and allow for future optimization of their overall health and development.

The specific aims are as follows:

1. To identify clinical factors that are associated with muscle and adipose tissue measurements. The investigators will examine the relationship between clinical factors such as calorie and protein intake during hospitalization, days on parenteral nutrition, C-Reactive Protein and other clinical surrogates for inflammation and both muscle and adipose tissue measured bi-weekly using bedside ultrasound. The investigators will collect anthropometric and ultrasound measurements bi-weekly and whole body composition (utilizing ADP) data at 35 weeks postmenstrual age (PMA)/discharge from the Neonatal Intensive Care Unit. All other clinical data will be collected throughout the hospital stay.
2. To determine whether muscle thickness and cross-sectional area are predictive of improved neurodevelopmental outcomes. The investigators will assess the relationship between ultrasound measurements of muscle with neurodevelopmental outcomes at 35 weeks PMA/discharge and 4 months corrected age. The investigators will utilize Event Related Potentials (ERP) to measure speed of processing and recognition memory as early markers of brain development.
3. To determine whether measurements of adipose tissue are predictive of later adverse metabolic outcomes. The investigators will assess the relationship between adipose tissue thickness and blood pressure and total body adiposity (using air-displacement plethysmography) at 35 weeks PMA/discharge and 4 months corrected age.

Inclusion Criteria:

• preterm infants born between 25 and 34+6 weeks gestation admitted to University of Minnesota Masonic Children's Hospital Neonatal Intensive Care Unit
• medically stable at time of air displacement measurements

Exclusion Criteria:

• infants that require medical support preventing ADP measurements from being taken

Preterm infants