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. About 1 in 10 babies are born prematurely each year in this country. 

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

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. About 1 in 10 babies are born prematurely each year in this country. 

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