Oxandrolone is an anabolic steroid, marketed in the United States as an adjunctive therapy to combat weight loss resulting from chronic infection, extensive surgery, severe trauma, protein catabolism associated with prolonged administration of corticosteroids, and for the relief of bone pain accompanying osteoporosis. In children, it has been used to prevent and treat growth failure associated with severe burns (≥ 40% of total body surface area), Duchenne muscular dystrophy, Turner's syndrome, constitutional delay of growth and puberty, and chronic wasting in HIV-positive pediatric patients. Other applications in children have included treatment of central idiopathic precocious puberty, hereditary angioedema, and bilateral congenital anorchia. Growth failure is a common feature of infants with complex congenital heart disease, and can adversely affect outcome. This therapy has not been previously implemented in neonates thus we will evaluate the safety and efficacy of administering oxandrolone to improve growth in neonates with complex congenital heart disease who have undergone surgical palliation or repair by collecting anthropometric measurements and pharmacokinetic data.