Surfactant is particularly important for survival of the premature infant. When surfactant is insufficient, the air-water (blood) surface membrane tension becomes high, bringing great risk that alveoli will collapse during expiration. As a result, respiratory distress syndrome (RDS) develops. This is a common cause of death in the premature infant. In these cases, the partially collapsed alveoli contain a fluid with a high protein content, many hyaline membranes, and lamellar bodies, probably derived from the surfactant layer. Respiratory Distress Syndrome, which is therefore also known as Hyaline Membrane Disease, accounts for approximatley 20% of deaths among newborns. Recent development of artificial surfactant and treatment of premature babies with glucocorticoids to stimulate surfactant production have reduced mortality associated with respiratory distress syndrome and allowed survival of some babies as young as 5.5 months of gestation.