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This topic covers preterm labor as it relates to the pregnant woman's problems and care. If you are looking for information about babies who are born too soon, see the topic Premature Infant. Labor and delivery before the end of 20 weeks of pregnancy is called a miscarriage. See the topic Miscarriage for more information.

What is preterm labor?

Preterm labor is the start of labor between 20 and 37 weeks of pregnancy. A full-term pregnancy lasts 37 to 42 weeks. In labor, the uterus contracts to open the cervix. This is the first stage of childbirth.

Preterm labor is also called premature labor.

What are the risks of preterm labor and preterm birth?

The earlier the delivery, the greater the risk for serious problems for the baby. This is because many of the organs-especially the heart and lungs-are not fully grown, or mature. Premature infants born after 32 weeks of pregnancy tend to have less chance of problems than those born earlier.

For infants born before 24 weeks of pregnancy, the chances of survival are extremely slim. Many who do survive have long-term health problems. They may also have other problems, such as trouble with learning and talking and with moving their body (poor motor skills).

What causes preterm labor?

Preterm labor can be caused by a problem with the baby, the mother, or both. Often the cause is not known.

Preterm labor most often occurs naturally. But sometimes a doctor uses medicine or other methods to start labor early because of pregnancy problems that are dangerous to the mother or her baby.

Causes of preterm labor include:

• The placenta separating early from the uterus. This is called placenta abruptio.
• Elevated blood pressure or pre-eclampsia.
• Being pregnant with more than one baby, such as twins or triplets.
• An infection in the mother’s uterus that leads to the start of labor.
• Problems with the uterus or cervix.
• Drug or alcohol use during pregnancy.
• The mother’s water (amniotic fluid) breaking before contractions start.

Treatments to help a woman get pregnant have led to more women being pregnant with more than one baby, such as twins or triplets. This has also increased the number of women who have preterm labor and preterm births.

What are the symptoms?

It can be hard to tell when labor starts, especially when it starts early. So watch for these symptoms:

• Regular contractions for an hour. This means about 4 or more in 20 minutes, or about 8 or more within 1 hour, even after you have had a glass of water and are resting.
• Leaking or gushing of fluid from your vagina. You may notice that it is pink or reddish.
• Pain that feels like menstrual cramps, with or without diarrhea.
• A feeling of pressure in your pelvis or lower belly.
• A dull ache in your lower back, pelvic area, lower belly, or thighs that does not go away.
• Not feeling well, including having a fever you can't explain and being overly tired. Your belly may hurt when you press on it.