A premature birth is a birth that takes place more than three weeks before the baby is due — in other words, after less than 37 weeks of pregnancy, which usually lasts about 40 weeks.

Premature birth gives the baby less time to develop in the womb. Premature babies, especially those born earliest, often have complicated medical problems.

Depending on how early a baby is born, he or she may be:

  • Late preterm, born between 34 and 37 weeks of pregnancy
  • Very preterm, born at less than 32 weeks of pregnancy
  • Extremely preterm, born at less than 25 weeks of pregnancy

Most premature births occur in the late preterm stage.

Dec. 29, 2011