Preterm labor

• Preterm labor and birth can happen to any pregnant woman.
• Women can take steps to reduce the risk of preterm labor.
• Learn the signs of preterm labor and what to do about them.

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Preterm birth is birth that happens before 37 completed weeks of pregnancy. This is too soon, and your baby could be born with serious health problems. Preterm labor is labor that happens before 37 completed weeks of pregnancy. If untreated, it can lead to preterm birth.

Preterm birth can happen to any pregnant woman. But it happens more often to some women than others. Researchers have found some risk factors for preterm birth, but they still can’t predict which women will give birth too early.

Having a risk factor doesn’t mean you definitely will have preterm birth. It just means you’re more likely than women who don’t have the risk factor to have your baby early.

Who is at risk for preterm birth?
Three groups of women are at greatest risk for preterm birth:

1. Women who have had a previous preterm birth
2. Women who are pregnant with twins, triplets or more
3. Women with certain uterine or cervical abnormalities

These groups of women are at increased risk of having preterm birth:

• African-American women 
• Women younger than 17 and older than 35 
• Women who have a low income 
• Women who are not married

If any of these groups describe you, talk to your health care provider about things you can do to help reduce your risk for preterm birth. Also, learn the signs of preterm labor and what to do if they happen to you.

Are there lifestyle and environmental risks for preterm birth?
Yes. Some studies have found that certain lifestyle factors may put you at greater risk of preterm birth. These include:

• Unintended pregnancy (This means you didn’t plan to get pregnant.) 
• Late or no prenatal care 
• Smoking 
• Drinking alcohol 
• Using street drugs 
• Exposure to the medication DES 
• Domestic violence, including physical, sexual or emotional abuse 
• Lack of social support 
• Stress 
• Long working hours with long periods of standing 
• Exposure to certain environmental pollutants

Are there medical risks for preterm birth?
Yes. Certain medical conditions during pregnancy may increase your chances of having preterm birth, including:

• Urinary tract infections, vaginal infections, sexually transmitted infections and, possibly, other infections, such as periodontal disease (gum disease) 
• Diabetes 
• High blood pressure and preeclampsia 
• Clotting disorders (thrombophilias) 
• Bleeding from the vagina 
• Certain birth defects in the baby 
• Being pregnant with one baby that is the result of in vitro fertilization (a kind of fertility treatment) 
• Being underweight before pregnancy 
• Poor weight gain during pregnancy in women who are not obese 
• Obesity (Obesity can lead to high blood pressure and preeclampsia. These conditions can increase your risk for preterm birth.) 
• Short time period between pregnancies (less than 6 to 9 months between pregnancies)

What can you do to reduce your risk for preterm birth?
Even if you have one of the risk factors for preterm birth, it doesn’t mean you will give birth early. It just means that you are more likely to have preterm birth than a woman who doesn’t have a risk factor. Still, knowing you're at risk can be scary.

Here’s what you can do to help reduce your risk for preterm birth. 

• Plan your pregnancy and visit a health care provider before you get pregnant. 
• Learn the signs of preterm labor and what to do if they happen to you. 
• Take good care of yourself and your baby while you're pregnant.

The March of Dimes is funding research to better understand risk factors and the causes of preterm birth.

See also: Premature birth, Progesterone treatment to prevent preterm birth, Why at least 39 weeks is best for your baby

Last reviewed October 2011