Two blood samples and two urine samples will be collected. The first one will be at 0 hour before starting TPN regimen as a base line and the second will be at 7 days of starting TPN regimen. Blood sample will be at least 1cc of blood for GSH/GSSG assay. Urine collection bag will be placed on the infant to obtain minimum of 1cc of urine for urinary peroxide level assay.