A premature baby is one who is born too early, before 37 weeks. Premature babies may have more health problems and may need to stay in the hospital longer than babies born later. 

They also may have long-term health problems that can affect their whole lives. About 1 in 10 babies is born prematurely each year in the United States. 

The earlier in pregnancy a baby is born, the more likely he is to have health problems. Some premature babies have to spend time in a hospital’s neonatal intensive care unit (also called NICU). This is the part of a hospital that takes care of sick newborns. But thanks to advances in medical care, even babies born very prematurely are more likely to survive today than ever before.