This topic covers how preterm labour 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.
Preterm labour is labour that comes too early—between 20 and 37 weeks of pregnancy.
Preterm labour is also called premature labour.
The earlier a baby is delivered, the higher the chances 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).
Causes of preterm labour include:
Often the cause isn't known.
Sometimes a doctor uses medicine or other methods to start labour early because of pregnancy problems that are dangerous to the mother or her baby.
It can be hard to tell when labour 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.
If you think you have symptoms of preterm labour, call your doctor or registered 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 labour.
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.
If you are in preterm labour, your doctor or registered midwife must compare the risks of early delivery with the risks of waiting to deliver. Depending on your situation, your doctor or midwife may:
Learning about preterm labour:
Preterm labour 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 labour include:
Preterm labour 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 labour contractions.
You may have one or more of these symptoms and not be in preterm labour. But if you are concerned, talk to your doctor or midwife.
If preterm labour 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 labour doesn't always mean that preterm birth will happen. Your doctor may be able to stop your preterm labour.
When preterm labour 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 caesarean section.
A baby born too early may have complications, such as anemia 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.
A risk factor is anything that increases your chances of having a problem.
Preterm labour can be hard to recognize. Get the earliest possible medical care by calling your doctor or your midwife about signs of preterm labour.
Call your doctor or your midwife if:
Call your doctor, your midwife, or the labour 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 midwife if you start to have regular contractions.
If you are in preterm labour, you may be seen by:
You may continue to see your registered midwife, who will consult with one of the doctors listed above.
To prepare for your appointment, see the topic Making the Most of Your Appointment.
If you have symptoms of preterm labour, both you and your baby will be examined and monitored.
Information from these examinations and tests can help you and your doctor or registered midwife decide whether to treat early labour and delay the birth or let it continue.
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 examinations or tests, including:
Preterm labour isn't always treated. When deciding whether—and how—to treat it, your doctor or registered 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 labour and delivery unit.
In the hospital, your doctor or midwife may use medicines to:
For more information, see Medications.
It's hard to prevent preterm labour, 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 labour and give your baby the best chance to be healthy.
Being pregnant with twins, triplets, or more increases the chances of preterm labour and problems for the babies.
If you had preterm labour 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 trimester. Research shows that these shots may help lower your risk of preterm labour.3, 4
More research is needed before other high-risk women, such as those who already have signs of preterm labour or women who are pregnant with twins or more, can be considered for progesterone treatment.
Symptoms of preterm labour 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 this:
Although stress isn't thought to be a direct cause of preterm labour, do what you can to reduce stress in your life for your own good. Try to do less, ask for help, and eat well.
Strict bedrest is no longer used to prevent preterm labour. But your doctor may recommend expectant management, which may involve some bedrest.
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 labour 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 pre-eclampsia, or poorly controlled diabetes or high blood pressure).
It isn't used to treat preterm labour. 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
|Society of Obstetricians and Gynaecologists of Canada (SOGC)|
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The mission of SOGC is to promote optimal women's health through leadership, collaboration, education, research, and advocacy in the practice of obstetrics and gynaecology.
- Haas DM (2010). Preterm birth, search date June 2009. Online version of BMJ Clinical Evidence: 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.
- Farine D, et al. (2008). The use of progesterone for prevention of preterm birth. SOGC technical update. Journal of Obstetrics and Gynaecology Canada, 30(1): 67–71. Also available online: http://www.sogc.org/guidelines/documents/guiJOGC202TU0801.pdf.
- American College of Obstetricians and Gynecologists (2008). Use of progesterone to reduce preterm birth. ACOG Committee Opinion No. 419. Obstetrics and Gynecology, 112: 963–965.
Other Works Consulted
- American College of Obstetricians and Gynecologists (1998). Premature rupture of membranes. ACOG Practice Bulletin No. 1. Obstetrics and Gynecology, 31(6): 1–10.
- Iams JD, et al. (2009). Preterm labor and birth. In RK Creasy et al., eds., Creasy and Resnik's Maternal Fetal Medicine, 6th ed., pp. 545–582. Philadelphia: Saunders Elsevier.
- McDonald S, et al. (2005). Perinatal outcomes of in vitro fertilization twins: A systematic review and meta-analyses. American Journal of Obstetrics and Gynecology, 193: 141–152.
- Murphy KE, et al. (2008). Multiple courses of antenatal corticosteroids for preterm birth (MACS): A randomised controlled trial. Lancet, 372(9656): 2143–2151.
- U.S. Preventive Services Task Force (2008). Screening for bacterial vaginosis in pregnancy to prevent preterm delivery: U.S. Preventive Services Task Force Recommendation Statement. Annals of Internal Medicine, 148(3): 214–219.
- Yost NP, et al. (2006). Effect of coitus on recurrent preterm birth. Obstetrics and Gynecology, 107(4): 793–797.
- Yudin M, et al. (2008). Screening and management of bacterial vaginosis in pregnancy. SOGC Guideline No. 211. Journal of Obstetrics and Gynaecology Canada, 30(8): 702–708. Available online: http://www.sogc.org/guidelines/documents/gui211CPG0808.pdf.
- Yudin M, et al. (2009). Antibiotic therapy in preterm premature rupture of the membranes. SOGC Guideline No. 233. Journal of Obstetrics and Gynaecology Canada, 31(9): 863–867. Available online: http://www.sogc.org/guidelines/documents/gui233CPG0909.pdf.
|Primary Medical Reviewer||Sarah Marshall, MD - Family Medicine|
|Specialist Medical Reviewer||William Gilbert, MD - Maternal and Fetal Medicine|
|Last Revised||August 10, 2012|
Last Revised: August 10, 2012
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