The 411 On Preterm Labor

stroking belly, close-up

From the March of Dimes

Preterm birth is any birth that occurs before the 37th week of pregnancy. It is the cause of many infant deaths and lingering infant illnesses in the United States. Every pregnant woman needs to know about preterm labor and birth—why it happens and what she can do to help prevent it.

Preterm birth occurs in about 12 percent of all pregnancies in the United States, often for reasons we just don’t understand. A normal pregnancy should last about 40 weeks. That amount of time gives the baby the best chance to be healthy. A pregnancy that ends between 20 weeks and 37 weeks is considered preterm, and all preterm babies are at significant risk for health problems. The earlier the birth, the greater the risk.

You might have read in the newspapers about babies who are born really early and do very well. But it’s important for you to know that those babies are the exceptions. Babies who are born very preterm are at a very high risk for brain problems, breathing problems, digestive problems, and death in the first few days of life. Unfortunately, they also are at risk for problems later in their lives in the form of delayed development and learning problems in school. The effects of premature birth can be devastating throughout the child’s life. The earlier in pregnancy a baby is born, the more health problems it is likely to have.

Why Does Preterm Labor Occur?
There are no easy answers. Stress might play a part for some women, personal health history or infection for others, or smoking or drug use for others. With funding from the March of Dimes and others, researchers are studying how various factors contribute to the complex problem of premature labor and birth.

Who Is at Risk for Preterm Labor?
Preterm labor and delivery can happen to any pregnant woman. But they happen more often to some women than to others. Researchers continue to study preterm labor and birth. They have identified some risk factors, but still cannot generally predict which women will give birth too early. Having a risk factor does not mean a woman will have preterm labor or preterm birth. It just means that she is at greater risk than other women.

Three groups of women are at greatest risk of preterm labor and birth:

-Women who have had a previous preterm birth

-Women who are pregnant with twins, triplets or more

-Women with certain uterine or cervical abnormalities

If you have any of these three risk factors, it’s especially important for you to know the signs and symptoms of preterm labor and what to do if they occur.

Lifestyle and Environmental Risks
Some studies have found that certain lifestyle and environmental factors may put a woman at greater risk of preterm labor. These factors include:

-Late or no prenatal care


-Drinking alcohol

-Using illegal drugs

-Exposure to the medication DES

-Domestic violence, including physical, sexual or emotional abuse

-Lack of social support


-Long working hours with long periods of standing

-Exposure to certain environmental pollutants