Preterm Labor

What is preterm labor?

Preterm labor is labor that starts before 37 completed weeks of pregnancy. Labor is when the uterus regularly tightens and the cervix starts to thin and open. This lets the baby (fetus) enter the birth canal.

What causes preterm labor?

For most people, the cause is unknown. Known causes of preterm labor are:

  • Infections

  • Vaginal bleeding

  • Hormone changes

  • Stretching of the uterus. This might be from being pregnant with more than 1 baby, a large baby, or too much amniotic fluid.

Who is at risk for preterm labor?

Most people who have preterm labor have no known risk factors. But some things raise a person's risk for preterm labor. These include:

  • Smoking

  • Being younger than 20 or older than 35

  • Long-term illness, such as heart disease or kidney disease

  • Using illegal drugs, such as cocaine

  • Abnormally shaped uterus

  • Cervix not able to stay closed

  • Stress

  • Having a preterm birth in the past

  • Being Black

  • Placenta that separates from the uterus early

  • Placenta in an abnormal position

  • Placenta that does not work as well as it should

  • Early breaking of sac around the baby (premature rupture of membranes)

  • Birth defects in the baby

  • Problems with fetal growth

  • More than one baby in the uterus

What are the symptoms of preterm labor?

These are the most common symptoms of preterm labor:

  • Tightening of the uterus (contractions), especially more than 4 in 1 hour

  • Menstrual-type cramps

  • Pressure in the lower belly

  • Backache

  • Diarrhea

  • Change in the type or amount of vaginal discharge. This might be blood, mucus, or watery fluid.

  • Gush of fluid from the vagina

If you have any symptoms of preterm labor, call your healthcare provider as soon as possible.

Some of these symptoms may be caused by other health conditions. Always see your healthcare provider for a diagnosis.

How is preterm labor diagnosed?

If your healthcare provider thinks you have preterm labor, you will likely be checked into the hospital. An electronic monitor is used to check how often contractions are happening and how long they last. This monitor has a small device (transducer) placed over your belly with a belt. The transducer detects and sends information about the contractions to the monitor. Your baby's heart rate is also often monitored.

Other ways of checking for preterm labor may include:

  • Cervical exam. Your healthcare provider may check your cervix for changes.

  • Transvaginal ultrasound exam. This ultrasound exam uses a device (transducer) placed inside the vagina. The exam lets your healthcare provider measure the length of your cervix.

  • Testing for amniotic fluid. This lets your provider know if the sac around the baby has broken.

  • Testing for fetal fibronectin (fFN). FFN is a protein found between the amniotic membrane and uterine lining. A swab of cervical or vaginal fluid is checked for fFN. If it's found, it may be a sign of preterm labor.

How is preterm labor treated?

Treatment for preterm labor may include:

  • Bed rest. This can be done either at home or in the hospital

  • Tocolytic medicines. These help slow or stop contractions. They may be given as a shot (injection) or into the vein (intravenously).

  • Corticosteroids. These may help the lungs of your baby grow and mature. Preterm babies’ lungs may not be able to work on their own.

  • Cervical cerclage. This procedure is used to stitch the cervix closed. It may be done when the cervix is weak and not able to stay closed.

  • Antibiotics. These are used to treat infection.

  • Delivery of the baby. Your provider will deliver your baby if treatments don't stop preterm labor or if you or your baby is in danger. You may need a cesarean section delivery.

What are possible complications of preterm labor?

Preterm labor may result in preterm birth. Although most babies are born after 37 weeks, those born preterm are at increased risk for many complications.

Premature babies are born before their body and organ systems have fully matured. These babies are often small, with a low birth weight (less than 2,500 grams or 5.5 pounds). They may also need help breathing, eating, fighting infection, and staying warm. Babies born before 28 weeks are at the greatest risk for problems.

Premature babies may have the following:

  • Trouble maintaining body temperature or staying warm

  • Breathing problems

  • Heart and blood vessels problems, including heart defects and blood and heart rate problems

  • Blood problems, including low red blood cell counts (anemia), yellow color to the skin from breaking down old red blood cells (jaundice), or low blood sugar (hypoglycemia)

  • Kidney problems

  • Digestive problems, including trouble feeding and poor digestion

  • Nervous system problems, including bleeding in the brain or seizures

  • Infections

Premature babies can have long-term health problems as well. Generally, the more premature the baby, the more serious and long-lasting are the health problems.

What can I do to prevent preterm labor?

More babies are surviving even though they are born early and are very small. It's best to prevent preterm labor if possible.

Prenatal care is important in finding problems and lifestyle factors that can increase the risks for preterm labor and birth. Here are ways to help prevent preterm labor:

  • If you smoke, get help to stop smoking before you become pregnant.

  • Find out if you're at risk for preterm labor.

  • Learn the symptoms of preterm labor.

If you are at high risk for preterm birth, your provider may give you the hormone progesterone. This medicine is inserted into your vagina. It helps reduce the risk for preterm birth if you've had a preterm birth in the past.

When should I call my healthcare provider?

During regular prenatal visits, you and your healthcare provider will talk about symptoms of preterm labor and normal labor. If you have any symptoms of preterm labor, including contractions, cramps, back pain, or leaking of fluid from your vagina, contact your healthcare provider right away.

Key points about preterm labor

  • Preterm labor is labor that starts before 37 weeks of pregnancy.

  • Symptoms include contractions, cramps, back pain, or leaking of fluid from the vagina.

  • Treatment may include bed rest, medicine, a procedure to stitch the cervix closed, or delivery of the baby.

  • Preterm labor may result in preterm birth. Babies born too early are at risk for many serious health problems.

  • If you have any symptoms of preterm labor, call your healthcare provider as soon as possible.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

  • Know the reason for your visit and what you want to happen.

  • Before your visit, write down questions you want answered.

  • Bring someone with you to help you ask questions and remember what your provider tells you.

  • At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

  • Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

  • Ask if your condition can be treated in other ways.

  • Know why a test or procedure is recommended and what the results could mean.

  • Know what to expect if you do not take the medicine or have the test or procedure.

  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.

  • Know how you can contact your provider if you have questions, especially after office hours or on weekends.

Online Medical Reviewer: Donna Freeborn PhD CNM FNP
Online Medical Reviewer: Heather M Trevino BSN RNC
Online Medical Reviewer: Tennille Dozier RN BSN RDMS
Date Last Reviewed: 2/1/2024
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