Health care providers consider labor to be preterm if it starts before 37 weeks of pregnancy. Because a fetus is not fully grown at 37 weeks, and it may not be able to survive outside the womb, health care providers will often take steps to stop labor if it starts before this time.

Despite attempts to stop labor, many cases of preterm labor end in premature birth. A baby born before 37 weeks of pregnancy is considered a preterm birth (or premature birth). Preterm births occur in about 12 percent of all pregnancies in the U.S. It is one of the top causes of infant death in this country.

For more information on preterm labor and birth, including some of the challenges faced by infants born preterm, please visit http://www.nichd.nih.gov/health/topics/Preterm_Labor_and_Birth.cfm.  

NICHD-supported research is looking into ways to help prevent preterm labor and birth, as well as to identify markers and predictors of preterm labor and premature birth. Much of the Institute's research on preterm labor and birth is supported by the Pregnancy and Perinatology Branch. The Branch provides scientific summaries of its research in its Report to the NACHHD Council (September 2008) and in the Prematurity Research at the NIH report. Please note that these publications are scientific in nature.

The NICHD's Division of Epidemiology, Statistics, and Prevention Research also conducts research in preterm labor and birth. NICHD news releases about preterm labor and birth provide more information about the Division’s efforts.

The following highlight other NICHD efforts related to understanding preterm labor and birth:

• NICHD Scientific Lead on Surgeon General's Conference on Preventing Preterm Birth
• Preventing Preterm Birth
• All NICHD News Release About Preterm Labor and Birth

Additional information about preterm labor and birth is available at http://www.nichd.nih.gov/health/topics/Preterm_Labor_and_Birth.cfm.