The length of time that a normal human pregnancy lasts (the full term of a pregnancy) is about 40 weeks, or just more than 9 months, from the start of the last menstrual (pronounced MEN-stroo-uhl) period to childbirth. Labor that begins before 37 weeks is called preterm labor (or early labor). An infant born before 37 weeks is considered a preterm birth.
Preterm birth is the most frequent cause of infant death and the leading cause of long-term neurological (nervous system) disabilities in children.1 Late-preterm birth refers to infants born from the 34th week of pregnancy to before the 37th week. More than 70% of preterm infants are born during this time. Although these infants typically do better than those born earlier, they are three times more likely to die in the first year of life than full-term infants.2
The NICHD is working hand in hand with other agencies and organizations to learn more about the causes of preterm labor and birth, reduce the number of preterm births, improve methods of predicting which women are at risk, and identify prevention methods. NICHD also is studying ways to improve care for infants born too early in order to reduce death and disability associated with preterm birth.
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Common Names
- Preterm labor or early labor
- Preterm birth or preterm delivery
Medical or Scientific Name
- Preterm (pronounced PREE-term) labor and birth