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This topic covers how preterm labor affects the pregnant woman. If you want to know how it affects the baby after he or she is born, see the topic Premature Infant.
What is preterm labor?
Preterm labor is labor that comes too early—between 20 and 37 weeks of pregnancy.
Preterm labor is also called premature labor.
What are the risks of preterm labor and preterm birth?
The earlier a baby is delivered, the higher the chances are that he or she will have serious problems. This is because many of the baby's organs—especially the heart and lungs—aren't fully grown yet.
For infants born before 24 weeks of pregnancy, the chances of survival are extremely slim. Many who do survive have long-term health problems. They may also have trouble with learning and talking and with moving their body (poor motor skills).
What causes preterm labor?
Causes of preterm labor include:
Often the cause isn't known.
Sometimes a doctor uses medicine or other methods to start labor early because of pregnancy problems that are dangerous to the mother or her baby.
What are the symptoms?
It can be hard to tell when labor starts, especially when it starts early. So watch for these symptoms:
If your contractions stop, they may have been Braxton Hicks contractions . These are a sometimes uncomfortable—but not painful—tightening of the uterus. They are like practice contractions. But sometimes it can be hard to tell the difference.
How is preterm labor diagnosed?
If you think you have symptoms of preterm labor, call your doctor or certified nurse-midwife. He or she can check to see if your water has broken, if you have an infection, or if your cervix is starting to dilate.
You may also have urine and blood tests to check for problems that can cause preterm labor.
Checking the baby's heartbeat and doing an ultrasound can give your doctor or midwife a good picture of how your baby is doing. Amniotic fluid can be tested for signs that your baby's lungs have grown enough for delivery.
You may have a painless swab test for a protein in the vagina called fetal fibronectin. If the test doesn't find the protein, then you are unlikely to deliver soon. But the test can't tell for certain if you are about to have a preterm birth.
How is it treated?
If you are in preterm labor, your doctor or certified nurse-midwife must compare the risks of early delivery with the risks of waiting to deliver. Depending on your situation, your doctor or midwife may:
Frequently Asked Questions
Preterm labor can be caused by a problem involving the baby, the mother, or both. Often a combination of several factors is responsible. But in about 1 out of 3 preterm births, the cause isn't known. 1
Causes of preterm labor include:
Preterm labor often starts without obvious symptoms. But you may notice one or more symptoms, including:
It is sometimes hard to tell the difference between Braxton Hicks contractions and preterm labor contractions.
You may have one or more of these symptoms and not be in preterm labor. But if you are concerned, talk to your doctor or nurse-midwife.
If preterm labor occurs close to your due date (in the 35th or 36th week of pregnancy), you may be allowed to deliver without delay. Preterm birth at this point in a pregnancy doesn't usually cause serious problems.
But preterm labor doesn't always mean that preterm birth will happen. Your doctor may be able to stop your preterm labor.
When preterm labor can't be stopped, most women can deliver vaginally. But if your health or your baby's health is at risk, you may need a cesarean section .
A baby born too early may have complications, such as bleeding in the brain or chronic lung disease. The earlier a baby is born, the higher the risk.
Your doctors can prepare you for what may lie ahead. They can base this on your condition and how many weeks pregnant you will be when you give birth.
Thanks to improved medical care, more premature infants are surviving today than in years past. For more information, see the topic Premature Infant.
What Increases Your Risk
A risk factor is anything that increases your chances of having a problem.
Risk factors related to your pregnancy
Risk factors related to your medical history
Other risk factors
When To Call a Doctor
Preterm labor can be hard to recognize. Get the earliest possible medical care by calling your doctor or your nurse-midwife about signs of preterm labor.
Anytime during your pregnancy
Call your doctor or your nurse-midwife if:
Between 20 and 37 weeks of your pregnancy
Call your doctor, your nurse-midwife, or the labor and delivery unit of your local hospital if:
If you are having painless or mild contractions that are irregular or more than 15 minutes apart:
If your contractions stop, they were probably Braxton Hicks contractions . These are harmless and normal. Braxton Hicks contractions are often irregularly timed and uncomfortable rather than painful.
Call your doctor or nurse-midwife if you start to have regular contractions.
Who to see
If you are in preterm labor, you may be seen by:
To prepare for your appointment, see the topic Making the Most of Your Appointment.
Exams and Tests
If you have symptoms of preterm labor, both you and your baby will be examined and monitored.
Information from these exams and tests can help you and your doctor or nurse-midwife decide whether to treat early labor and delay the birth or let it continue.
For the mother
You will be examined for tenderness in your uterus. Your temperature, pulse, and rate of breathing will be checked. Depending on your symptoms, you may have one or more exams or tests, including:
For the baby
Preterm labor isn't always treated. When deciding whether—and how—to treat it, your doctor or nurse-midwife will think about:
If your water hasn't broken, you will be observed for at least an hour or two to see if your contractions continue and your cervix changes (opens and thins). If your cervix doesn't change, or if your contractions stop or slow down, you may be sent home.
If your cervix changes, you will be admitted to the labor and delivery unit.
In the hospital, your doctor or nurse-midwife may use medicines to:
For more information, see Medications.
It's hard to prevent preterm labor, because it usually isn't expected. Also, it's often due to causes that aren't completely understood.
But building some healthy pregnancy habits—such as going to all of your doctor appointments and getting enough folic acid— may help prevent preterm labor and give your baby the best chance to be healthy.
Being pregnant with twins, triplets, or more increases the chances of preterm labor and problems for the babies.
If you had preterm labor in a previous pregnancy, your risk for having it again is high. Your doctor may consider giving you weekly progesterone shots during your second and third trimesters. Research shows that these shots may help lower your risk of preterm labor. 3
But if you're pregnant with twins or more, progesterone treatment is generally not used to prevent preterm labor even if you had a previous preterm birth. Research has not shown that progesterone shots prevent preterm birth in women pregnant with more than one baby. 4
Symptoms of preterm labor are warning signs. They don't necessarily mean that you'll have a preterm birth.
If you're less than 37 weeks pregnant and you're having more or stronger contractions than usual, try these things:
Although stress isn't thought to be a direct cause of preterm labor, do what you can to reduce stress in your life. Try to do less, ask for help, and eat well.
Strict bed rest is no longer used to prevent preterm labor. But your doctor may recommend expectant management, which may involve some bed rest.
If your contractions are causing changes in your cervix, or if you have signs of infection or preterm premature rupture of membranes (pPROM), you may be given medicines to help delay delivery.
Delaying labor even for a short time can allow you to be:
Certain tocolytic medicines can be dangerous when a fetus is showing signs of distress or for women with certain health conditions (such as heart problems, severe preeclampsia, or poorly controlled diabetes or high blood pressure).
It isn't used to treat preterm labor. But for a woman who has had a preterm birth in the past because her cervix didn't stay closed, cervical cerclage may prevent another preterm birth. 1
Other Places To Get Help
Last Revised: January 8, 2013
Haas DM (2011). Preterm birth, search date June 2010. BMJ Clinical Evidence. Available online: http://www.clinicalevidence.com.
Samson SA, et al. (2005). The effect of loop electrosurgical excision procedure on future pregnancy outcomes. Obstetrics and Gynecology, 105(2): 325–332.
American College of Obstetricians and Gynecologists (2012). Prediction and prevention of preterm birth. ACOG Practice Bulletin No. 130. Obstetrics and Gynecology, 120(4): 964–973.
American College of Obstetricians and Gynecologists (2012). Management of preterm labor. ACOG Practice Bulletin No. 127. Obstetrics and Gynecology, 119(6): 1308–1317.
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