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Preterm labor

  • Preterm labor can happen to any pregnant woman.
  • Some women have a higher risk than others.
  • Learn the signs of preterm labor.
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Preterm labor and premature birth

Preterm labor is labor that happens too early, before 37 weeks of pregnancy. Preterm labor can lead to premature birth. This means your baby is born before 37 weeks of pregnancy. Babies born this early can face serious health problems. Each year in this country, about 380,000 babies are born prematurely. 

What causes preterm labor and birth?

Sometimes we don’t know for sure what causes preterm labor and premature birth. Any woman can have preterm labor and give birth early, even if she’s done everything right during pregnancy.

We do know some things make a woman more likely than others to have preterm labor and premature birth. These are called risk factors. Having a risk factor doesn’t mean for sure that you’ll have preterm labor or give birth early. But it may increase your chances. Talk to your health provider about what you can do to help reduce your risk.

Because many premature babies are born with low birthweight, many risk factors for preterm labor and premature birth are the same as for having a low-birthweight baby. Low birthweight is when a baby is born weighing less than 5 pounds, 8 ounces.

These three risk factors make you most likely to have preterm labor and give birth early:

  1. You’ve had a premature baby in the past
  2. You’re pregnant with multiples (twins, triplets or more).  
  3. You have problems with your uterus or cervix now or you’ve had them in the past.

Medical risk factors for preterm labor and premature birth

  • Getting late or no prenatal care. Prenatal care is medical care you get during pregnancy.
  • Bleeding from the vagina in the second or third trimester 
  • Being underweight or overweight before pregnancy or not gaining enough weight during pregnancy
  • Having certain health conditions, like high blood pressurepreeclampsiadiabetes or thrombophilias (blood clotting disorders). Or having certain infections during pregnancy, like a sexually transmitted disease (STD) or other infections of the uterus, urinary tract or vagina. 
  • Preterm premature rupture of the membranes (also called PPROM). This is when the sac around the baby breaks early, causing labor to start. 
  • Being pregnant after in vitro fertilization (IVF). IVF is a fertility treatment used to help women get pregnant.  
  • Being pregnant with a baby who has certain birth defects, like congenital heart defects or spina bifida
  • Getting pregnant too soon after having a baby. For most women, it’s best to wait 18 to 23 months before getting pregnant again. Some women can’t wait this long because of their age or other reasons. Talk to your provider about what’s right for you. 
  • Having a family history of premature birth. This means someone in your family (like your mother, grandmother or sister) has had a premature baby. If you were born prematurely, you’re more likely than others to give birth early. 
  • Exposure to the medicine DES, a man-made form of the hormone estrogen. This includes being exposed to DES in the womb (your mother took DES when she was pregnant with you).

Risk factors in your everyday life for preterm labor and premature birth

Other risk factors for preterm labor and premature birth: Age and race/ethnicity 

Being younger than 17 or older than 35 makes you more likely than other women to give birth early. And race/ethnicity is a risk factor, too. In the United States, black women are more likely to give birth early. Almost 17 percent of black babies are born prematurely each year. Just more than 10 percent of Native American and Hispanic babies are born early, and less than 10 percent of white and Asian babies. We don’t know why race plays a role in premature birth; researchers are working to learn more about it.   

What are the signs of preterm labor?

We know that preterm labor can lead to early birth. So how do you know if you’re in preterm labor? Learn the signs of preterm labor so you know what to do if preterm labor happens to you.

Are there treatments for preterm labor?

Yes. You may get treatments to help prevent or stop preterm labor. Or you may get treatments to help improve your baby's health before birth. Talk to your provider about which treatments may be right for you. 

Last reviewed October 2014

Signs of preterm labor

  • Contractions every 10 minutes or more often
  • Change in vaginal discharge
  • Pelvic pressure
  • Low, dull backache
  • Cramps that feel like your period
  • Abdominal cramps with or without diarrhea

Frequently Asked Questions

Am I at risk for preterm labor?

No one knows for sure what causes a woman to have preterm labor. But if you have certain risk factors, you're more likely than a woman without risk factors to have preterm labor. Risk factors include: having already had a premature baby or getting pregnant again too soon after having a baby; being pregnant with twins or more; and having problems with your uterus or cervix. You're more likely to have preterm labor if you're underweight or overweight or if you have health problems, like high blood pressure, diabetes or certain infections. Things in your life like stress, smoking, drinking alcohol and using drugs also put you at risk. Talk to your provider if you have any of these risk factors. You may be able to reduce your risk and have a better chance for a healthy pregnancy.

How do I know I’m in labor?

You'll know you're in labor if:

  • You have strong and regular contractions that last 30 to 60 seconds and come 5 to 10 minutes apart.
  • Your water breaks. Your baby has been growing in amniotic fluid (bag of waters) in your uterus. When the bag of waters breaks you may feel a big rush of waters or you may feel just a trickle.
  • You bleed a little from your vagina. This is called bloody show.

If you think you're in labor, call your health care provider, no matter what time of day or night.

How early can a baby be born and live?

There is no set timeline for survival for babies born early. Babies born earlier than 23 weeks have a much smaller chance of survival than babies born after 23 weeks.

About 9 out of 10 babies born at 28 weeks survive. But many have serious health problems. Any baby born before 37 weeks of pregnancy is considered premature. Premature babies have less time to develop in the womb than babies who arrive on time. This puts them at greater risk of medical and developmental problems. Every extra day in the womb helps the baby develop and mature and probably improve his or her health and development later in life. Between 23 and 26 weeks, every extra day in the womb increases a baby's chance of survival by 2 to 4 percent.

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