Preterm Labor

Preterm labor is when your body prepares to give birth too early, before 37 weeks of pregnancy. Premature labor does not always lead to birth. In some cases, your doctor can delay birth using medicines. In other instances, early labor stops on its own.

Sometimes, the safest option for your health and your baby's is to deliver early. A premature baby is at an increased risk of long-term, serious health problems.

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On this page:

• What Is Preterm Labor?
• What Are the Symptoms of Preterm Labor?  
• How Do You Diagnose Preterm Labor? 
• How Do You Treat Preterm Labor?

What Is Preterm Labor?

Preterm labor is when your body gets ready to give birth too early. During labor, the uterus contracts to open the cervix. This is the first stage of childbirth.

In most pregnancies, labor starts between 37 and 42 weeks. In preterm labor, labor begins between 20 and 37 weeks of pregnancy. When labor starts before 20 weeks, the pregnancy loss is considered a miscarriage.

Preterm labor does not always lead to preterm birth. Your body may stop labor on its own. Or your doctor may be able to stop preterm labor with medications.

When preterm labor doesn't stop, most people can deliver vaginally. In an emergency that threatens your health or your baby's health, you may need a C-section.

A baby born prematurely (too early) can have serious, long-term health problems. Among these problems are complications with the heart, lungs, or brain because many of the baby's organs aren't fully grown yet. 

A premature baby also is at an increased risk of autism, intellectual disabilities, cerebral palsy, vision impairment, and hearing loss. The earlier a baby is born, the higher the risk of problems. However, many preterm babies will catch up to their full-term peers with time despite these risks.

What causes preterm labor?

The cause of preterm labor is often a problem involving the baby, the pregnant person, or both. Often, a mix of factors is responsible. Sometimes, pinpointing a specific cause of preterm labor can be hard.

Possible causes of preterm labor include:

• An infection in the uterus.
• A multiple pregnancy, such as twins or triplets.
• Drug or alcohol use during pregnancy.
• Placental abruption, in which the placenta separates from the uterus.
• Problems with the uterus or cervix.
• Your amniotic (water) sac breaks too early.

Preterm labor risk factors and complications

You may be at a higher risk of preterm labor if you:

• Are dealing with physical, sexual, or emotional abuse.
• Are diabetic.
• Are exposed to air pollution, lead, radiation, harmful chemicals, plastics, or secondhand smoke.
• Are of low socioeconomic status.
• Are Black, although researchers don't know why.
• Are pregnant due to in vitro fertilization.
• Are pregnant with a baby who has congenital disabilities such as heart defects or spina bifida.
• Are pregnant with multiples, such as twins or triplets.
• Are on your feet for a large portion of the day.
• Are under a lot of stress.
• Are younger than 17 or older than 35.
• Become pregnant again within 18 months of having a baby.
• Bleed from your vagina during the second or third trimester of pregnancy.
• Did not gain enough weight during pregnancy.
• Have a connective tissue disorder.
• Have a family or personal history of preterm labor.
• Have a short cervix (20 mm or less).
• Have an eating disorder, such as anorexia or bulimia.
• Have high blood pressure.
• Have an infection of the uterus, urinary tract, or vagina, including sexually transmitted infections.
• Have intrahepatic cholestasis of pregnancy, a liver condition that may develop during pregnancy.
• Have preeclampsia, which is high blood pressure with protein in your urine during pregnancy.
• Have preterm premature rupture of the membranes, meaning that your water breaks too early.
• Have problems with your uterus or cervix.
• Have substance abuse issues, especially smoking, using cocaine or crack, or abusing prescription drugs.
• Have a blood clotting disorder.
• Received prenatal care too late in pregnancy, did not receive prenatal care at all, or received poor quality prenatal care.
• Were born prematurely yourself.
• Were very overweight or underweight before pregnancy.

How to prevent preterm labor

The only way to reduce your risk of preterm labor is to maintain healthy habits during pregnancy. A healthy pregnancy will also give your baby the best chance to be healthy.

To reduce your risk of preterm labor, you can try the following:

• Get prenatal care as soon as you know you're pregnant. Regularly attend all prenatal checkups during pregnancy.
• Be active every day.
• Eat healthy foods.
• Maintain a healthy weight before pregnancy and gain the right amount of weight during pregnancy.
• Ask for help if you are in an abusive situation.
• Protect yourself from infections with vaccines, frequent hand washing, practicing safe sex, avoiding cat feces, and not eating raw meat, fish, or eggs.
• Reduce stress as much as possible.
• Take care of your chronic health issues, such as high blood pressure, diabetes, depression, or thyroid problems.
• Stop smoking, drinking, or using drugs.
• Wait at least 18 months after giving birth to get pregnant again.

If you had preterm labor in a previous pregnancy, your risk of having it again is high. Your doctor may give you a hormone medicine called progesterone to lower your risk of preterm labor.

Progesterone does not prevent preterm birth in people pregnant with multiples. If you're pregnant with twins or more, your doctor won't typically give you progesterone, even if you had a previous preterm birth.

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What Are the Symptoms of Preterm Labor?  

The symptoms of preterm labor include:

• Backache.
• Contractions.
• Cramping.
• Diarrhea.
• Fluid leaking from your vagina (your water breaking).
• Nausea or vomiting.
• Increased pressure in your pelvis, belly, or vagina.
• Increased vaginal discharge or changes in vaginal discharge.
• Vaginal bleeding in any amount.

It can be hard to tell when labor starts. Watching for warning signs of early labor can greatly decrease your chances of early delivery. If you are experiencing preterm labor, contact your doctor right away. 

If you notice one or more of the following symptoms, you may be going into labor:

• Pressure in your lower belly.
• A persistent, dull ache in your abdomen, lower back, pelvic area, or thighs.
• Increase or color change (pink or reddish) in your vaginal discharge.
• Leaking or gushing pink or reddish fluid from your vagina.
• Menstrual-like cramps. You may also have diarrhea.
• Six or more contractions in one hour, especially after a glass of water and resting. Contractions may not be painful yet, but your belly will feel tight like a fist.

What do preterm labor contractions feel like?

If your contractions are mild and stop, they may have been Braxton Hicks. These are harmless and normal uterine tightenings that don't dilate the cervix. You can think of them as "warm-up" exercises for your uterus. 

Preterm labor contractions will feel stronger, more painful, and more regular than Braxton Hicks contractions. They'll come closer together the longer you wait.

It can be difficult to tell the difference between Braxton Hicks contractions and actual labor. Braxton Hicks are more irregular, vary in strength, and are generally not painful. They often go away when you change position and are more noticeable when resting. They typically just feel uncomfortable and occur less than four times an hour.

If you're having more or stronger contractions than usual, try these things:

• Reduce your stress levels — try to do less, ask for help, and eat well.
• Drink two or three glasses of water — dehydration can cause contractions.
• Lie down and rest on your left side for at least one hour.

If your contractions are worse after these interventions, call your women's health provider or go to the hospital.

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How Do You Diagnose Preterm Labor? 

Call your prenatal care team if you're having symptoms of preterm labor. They'll ask you questions and determine if you need to go to the hospital.

If they're worried about preterm labor, they'll have you come to labor and delivery and monitor you and your baby. They'll check your cervix (the opening to your uterus) to see if it is starting to open.

Your doctor will check your baby's heartbeat and perform an ultrasound to check your amniotic fluid levels. If you are having contractions, your doctor will monitor their intensity and frequency.

Your doctor may conduct urine and blood tests to check for problems, like infections, that can cause preterm labor. They may check the fluid in your vagina to see if your water has broken.

Your doctor may swab the vagina for the protein fetal fibronectin. The presence of fetal fibronectin suggests you will deliver soon. The test can't tell for sure if you are about to have a preterm birth, though.

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How Do You Treat Preterm Labor?

Your doctor won't always treat preterm labor. They will consider your health and your baby's age, weight, and health when deciding if they need to stop labor or prepare for delivery.

If preterm labor occurs in the 35th or 36th week, your doctor may be okay with you delivering. When you're this close to your due date, complications from preterm birth aren't usually serious.

Your doctor will compare the risk of early delivery with the risks of stopping labor. If your contractions are causing changes in your cervix, you have signs of infection, or your water has broken, they may give you medicine to help stop or delay delivery.

To stop preterm labor or delay delivery, your doctor may:

• Treat the issues that are causing trouble in the pregnancy.
• Try to stop or delay labor with tocolytic medicines to stop preterm labor, which may or may not work. Certain tocolytic medicines can be dangerous to a fetus in distress or a pregnant person with health issues. Tocolytics include:
  • Beta-adrenergic receptor agonists, such as terbutaline.
  • Nonsteroidal anti-inflammatory drugs, such as indomethacin.
  • Calcium channel blockers, such as nifedipine.
• Use antibiotics to prevent infection. If your water breaks early, you have a high risk of infection. The doctors will watch you closely while delaying or stopping labor.

If your labor doesn't stop or your doctor thinks using tocolytics is too risky based on other health issues, they may start to prepare for your baby to be born.

To prepare for birth, your doctor may:

• Prepare your baby's lungs for birth with steroid medicines. These medicines take 48 hours to fully benefit the baby's lungs, but even 24 hours helps.
• Move you to a medical center that has a neonatal intensive care unit that's right for your preterm baby.
• Give you magnesium sulfate to delay labor and reduce the risk of problems that affect a premature baby's brain, such as cerebral palsy.

By UPMC Editorial Staff. Last reviewed on 2024-09-05.