Almost 1 of every 10 infants born in the United States are premature, or preemies. A premature birth is when a baby is born before 37 completed weeks of pregnancy. A full-term pregnancy is 40 weeks.
Important growth and development happen throughout pregnancy - especially in the final months and weeks. Because they are born too early, preemies weigh much less than full-term babies. They may have health problems because their organs did not have enough time to develop. Problems that a baby born too early may have include
Preemies need special medical care in a neonatal intensive care unit, or NICU. They stay there until their organ systems can work on their own.
Centers for Disease Control and Prevention