Keeping Preemies Warm Premature babies—born three or more weeks short of a full-term pregnancy—often lack vital body fat, putting them at risk of dangerously low body temperatures. Such "preemies" can be warmed in hospital incubators. However, incubators are not always a viable solution in lower-income countries. Hospitals in poor countries often cannot afford the equipment, and the hospitals that do have incubators are typically located only in urban areas. Many rural families are unable to transport their preemies such long distances, and those who make the trip can generally remain at the hospital for only a few days. A group of students at Stanford University developed a solution: an inexpensive, portable baby warmer for home-based use. Similar to a small sleeping bag, the warmer contains a heating pouch which, once warmed, maintains a temperature of 98.6°F for four hours. Thanks to this innovation, thousands of preemies have been saved.
What is the main, or central, idea of the passage?