Preterm labor happens when regular contractions cause the cervix to open after week 20 and before week 37 of pregnancy.

Preterm labor can result in a baby being born before 37 weeks of pregnancy. The earlier the delivery, the greater the health risks for the baby. Many premature babies, called preemies, need special care in a neonatal intensive care unit. Preemies also can have long-term mental and physical health concerns.

The cause of preterm labor often isn't clear. Certain risk factors can raise the chance of preterm labor. But preterm labor can happen with no known risk factors.

Symptoms of preterm labor include:

• Regular or frequent feelings of belly tightening, called contractions.
• Dull low backache.
• A feeling of pressure in the pelvis or lower belly.
• Mild belly cramps.
• Vaginal spotting or light bleeding.
• A gush or an ongoing trickle of fluid after the sac around the unborn baby, called the fetus, breaks or tears.
• Fluid from the vagina that is watery, bloody or filled with mucus.

When to see a doctor

If you have symptoms of preterm labor or you're worried about how you feel, contact your healthcare professional right away. Your healthcare professional can find out if you're in preterm labor or rule it out. Ruling it out could ease your mind.

Preterm labor can affect any pregnancy. But many factors can raise the risk of preterm labor. They include the following.

Medical history

• Preterm labor or premature birth in an earlier pregnancy. The risk is greater if this happened in the most recent pregnancy or in more than one pregnancy.
• Shortened cervix.
• Issues with the uterus or placenta.
• Certain infections. This is mainly true of infections of the amniotic fluid and lower genital tract.
• Some ongoing conditions, called chronic conditions. These include high blood pressure, diabetes, autoimmune disease and depression.

Pregnancy issues

• Pregnancy with twins, triplets or other multiples.
• Too much amniotic fluid. The medical term for this is polyhydramnios.
• Vaginal bleeding during pregnancy.
• Less than 18 months between pregnancies.
• Pregnancy before age 17 or after age 35.
• Pregnancy by way of assisted reproductive technology. This increases the risk of preterm labor whether it results in one fetus or more.

Other factors

• Smoking or illegal drug use.
• Stressful life events, such as the death of a loved one.
• Black race, non-Hispanic ethnicity.
• Poor nutrition or low pre-pregnancy weight.
• Lack of prenatal care.

Complications of preterm labor include having a premature baby. A baby who is born too early can have health issues. These may include low birth weight, trouble breathing, organs that are not fully formed, and trouble seeing and hearing.

Children who are born too early also have a higher risk of cerebral palsy, learning disabilities and behavioral problems. And preterm birth can be fatal for the baby.

You might not be able to prevent preterm labor. But you can do things to support a healthy, full-term pregnancy. For example:

• Get regular prenatal care. Prenatal visits allow your healthcare professional to watch your health and your baby's health. At those visits, talk about any symptoms that worry you. If you have a history of preterm labor or have symptoms of preterm labor, you might need to see your health professional more often during pregnancy.
• Eat well. Healthy pregnancy outcomes often are linked with healthy eating.
• Don't use unhealthy substances. If you smoke, quit. Ask your healthcare professional about ways to help you quit. Don't use illegal drugs, either.
• Think about pregnancy spacing. Some research suggests a link between premature birth and pregnancies that start six months or less after the last delivery. Talk with your healthcare team about pregnancy spacing and birth control.
• Manage ongoing health conditions. Certain conditions that are ongoing, also called chronic, may raise the risk for preterm labor. Examples include diabetes, high blood pressure and obesity. Work with your healthcare team to control chronic conditions.

If you have a history of preterm labor or premature birth, you're at risk of preterm labor in later pregnancies. Work with your healthcare team to manage risk factors and respond to early symptoms of preterm labor.

Your healthcare professional reviews your medical history, your risk factors for preterm labor and your symptoms. If you have regular uterine contractions and your cervix starts to soften, thin and open, called dilate, before 37 weeks of pregnancy, you likely are in preterm labor.

Tests and procedures to diagnose preterm labor include:

• Pelvic exam. This exam looks at how firm and tender your uterus is. It's done if your water hasn't broken and there's no worry that the placenta is covering the cervix. That condition is called placenta previa. Your healthcare professional does a pelvic exam to see if your cervix has started to open and to check for uterine bleeding.
• Ultrasound. A transvaginal ultrasound can measure the length of your cervix. An ultrasound also can show the fetus's size and position. And it can check for issues with the fetus or placenta and show the volume of amniotic fluid.
• Uterine monitoring. A uterine monitor measures how long your contractions last and how far apart they are.
• Lab tests. Your healthcare professional might take a swab of your vagina to check for certain infections and a substance called fibronectin. That substance acts like glue between the fetal sac and the lining of the uterus. It's released during labor. Your healthcare professional reviews these results with other risk factors. A urine sample can show certain bacteria.

If you're at risk of preterm labor, your healthcare team may suggest ways to keep labor from starting too soon.

Surgical procedure

During a procedure called cervical cerclage, the cervix is stitched closed with strong sutures. Most often, a member of your healthcare team removes the sutures after 36 weeks of pregnancy. If needed, the sutures can be removed earlier.

Cervical cerclage may be used for people who are less than 24 weeks pregnant, who have a history of early premature birth, and who have a cervix that is opening or a cervical length that is less than 25 millimeters, called a short cervix.

Vaginal progesterone

For a short cervix diagnosed before 24 weeks of pregnancy, progesterone that goes into the vagina might lower the risk of preterm birth.

Treatments once you're in labor

No medicines or surgeries can stop labor, except briefly. But your healthcare team might suggest the following medicines:

• Corticosteroids. Corticosteroids can help lower health risks when a baby is born preterm. This includes lowering the baby's risk of lung problems, bleeding in the brain, severe infection, called sepsis, and even death. Your healthcare team likely will suggest corticosteroids if you are less than 37 weeks pregnant and thought to be at higher risk of delivery in the next 1 to 7 days.
• Magnesium sulfate. Your healthcare team might offer magnesium sulfate if you have a high risk of delivering between weeks 24 and 32 of pregnancy. Some research has shown that it might lower the risk of a certain type of damage to the brain, called cerebral palsy, for babies born before 32 weeks.

• Tocolytics. These medicines can slow contractions for a while. Tocolytics can delay preterm labor for 48 hours. This delay can give corticosteroids time to work. Or, if needed, the delay gives you time to get to a hospital that can treat premature babies.

  Tocolytics don't treat the cause of preterm labor. And they don't improve the outcomes for babies. You won't get a tocolytic if you have certain conditions, such as pregnancy-induced high blood pressure, called preeclampsia.

If you're at risk of preterm labor and you're not in a hospital, you might need to see your healthcare team weekly or more often. This is so your team can watch for symptoms of preterm labor.

Preterm contractions might be Braxton Hicks contractions. These are common. They don't mean that your cervix has started to open. If you feel contractions, try walking, resting or changing positions. This might stop Braxton Hicks contractions. If you're in true preterm labor, the contractions keep going.

Bed rest to manage preterm labor has not been shown to lower the risk of preterm birth. Bed rest can lead to blood clots, emotional distress and muscle weakness.

If you're at risk of preterm labor or premature birth, you might worry during your pregnancy. You might worry more if you have a history of preterm labor or premature birth. Talk with your healthcare team about ways to relax and stay calm.

If you have symptoms of preterm labor, contact your healthcare professional right away. You might need medical care right away.

Here's some information to help you get ready for your appointment.

What you can do

Before your appointment, you might want to:

• Ask what you need to do before the appointment. You may get in to see your healthcare team right away. If not, ask whether you should limit your activity while you wait for your appointment.
• Ask a loved one or friend to join you for your appointment. A support person can help you remember all the information you get.
• Write down questions to ask your healthcare team. That way, you won't forget what you want to ask.

Some basic questions to ask your healthcare team include:

• Am I in labor?
• Is there anything I can do to keep from delivering early?
• Are there any treatments that could help the baby?
• What symptoms should I contact you about?
• What symptoms should make me go to the hospital?
• What are the risks if my baby is born now?

Be sure to ask all the questions you have.

What to expect from your doctor

Be ready to answer questions such as:

• When did you notice your symptoms?
• Are you having contractions? If so, how many an hour?
• Have you had changes in vaginal discharge or bleeding?
• Have you been around someone with an infectious disease? Do you have a fever?
• Have you had other pregnancies, miscarriages, or cervical or uterine surgeries that aren't in your record?
• Do you or did you smoke? How much?
• How far do you live from the hospital?
• How long would it take you to get to the hospital in an emergency? Include time to arrange child care or a ride.

Preterm labor puts your baby at risk. Work with your healthcare team to improve your chance of a healthy outcome.