Preterm labor and birth

Preterm labor is labor that happens too early, before 37 completed weeks of pregnancy. Preterm labor can lead to preterm birth (also called premature birth). This means your baby is born before 37 completed weeks of pregnancy. Babies born this early can face serious health problems. Nearly half a million 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 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 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.

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

  1. Having a premature baby in the past
  2. Being pregnant with multiples (twins, triplets or more)
  3. Having problems with your uterus or cervix now or in the past

Other risk factors for preterm labor and birth are:

Medical conditions

  • Bleeding from the vagina in the second or third trimester
  • Being under- or overweight before pregnancy
  • Not gaining enough weight during pregnancy
  • Certain health conditions, like high blood pressure, preeclampsia, diabetes or thrombophilias (blood clotting disorders)
  • Preterm labor
  • Preterm premature rupture of the membranes (also called PPROM). This is when the sac around the baby breaks early, causing labor to start.
  • Certain infections during pregnancy, like a sexually transmitted infection (STI) or other infections of the uterus, urinary tract or vagina.
  • Being pregnant with just one baby after in vitro fertilization (IVF) fertility treatment. IVF is a method used to help women get pregnant.
  • Getting pregnant too soon after having a baby. For most women, it’s best to wait at least 18 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.
  • Being pregnant with a baby who has certain birth defects, like congenital heart defects or spina bifida
  • A family history of premature birth. This means that someone in your family has had a premature baby.
  • Exposure to the medicine DES, a man-made form of the hormone estrogen

Conditions in your everyday life (lifestyle and environment)

Groups at increased risk

  • Women who are younger than 17 or older than 35
  • Women who are black
  • Women with low income or education Women who aren’t married

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. These treatments are not a guarantee to stop preterm labor. But if you’re having preterm labor, they may help you stay pregnant longer. Talk to your provider to find out if these treatments are right for you:

  • Progesterone. This is a hormone that’s normally present in the body. Treatment with progesterone during pregnancy may help reduce the risk of giving birth early.
  • Cerclage. This is a stich that your provider puts in your cervix. The stich may help keep your cervix closed so that your baby isn’t born too early. Your provider removes the stich at about 37 weeks of pregnancy. A cerclage is only used for certain women. For example, if you have a condition called cervical insufficiency, you may need a cerclage.

If you have signs of preterm labor, your provider may want you to have the fFN test. fFN stands for fetal fibronectin. It’s a protein that your body makes during pregnancy.

The fFN test is like a Pap smear. It checks to see how much fFN is in your vagina. If the test shows you don’t have any fFN, you probably won’t have your baby for at least another 2 weeks.

If you have preterm labor, your provider may give you treatments to try to stop your contractions and help prevent health problems in your baby. These include:

  • Corticosteroids. These medicines speed up your baby’s lung development. They also greatly reduce the risk of health problems in your baby, like respiratory distress syndrome and intraventricular hemorrhage.
  • Tocolytics. These medicines may postpone labor, often for just a few days. This delay may give you time to get treatment with corticosteroids and arrange to have your baby in a hospital with a neonatal intensive care unit (NICU). This is part of a hospital that takes care of sick newborns.
  • Magnesium sulfate. This medicine may help reduce the risk for cerebral palsy in premature babies. However, magnesium sulfate shouldn’t be used for more than 5 to 7 days. Using this medicine longer than that may lessen the amount of calcium in your growing baby and lead to bone problems.

Last reviewed June 2013

See also: Peterm labor: What dads can do

Most common 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 completed 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.

©2013 March of Dimes Foundation. The March of Dimes is a non-profit organization recognized as tax-exempt under Internal Revenue Code section 501(c)(3).