Premature baby. View of a premature baby in an incubator with a respirator (upper left) and a nasogastric tube attached to its nose. The incubator provides the baby with the ideal environment for survival, while the respirator ensures the baby receives sufficient oxygen despite its immature lungs. Premature babies must first be fed using a nasogastric tube as they have no sucking reflex and only poor swallowing ability. Babies such as this are usually kept in hospital until they weigh about 2.25 kg and are feeding well.