Birth is considered premature, or preterm, when it occurs before the 37th week of pregnancy. A normal pregnancy lasts about 40 weeks.
Those final weeks in the womb are crucial for healthy weight gain and for the full development of various vital organs, including the brain and lungs. This is why premature babies may have more medical problems and may require a longer hospital stay. They may also have long-term health issues, such as learning disabilities or physical disabilities.