Preterm Labour

Search Knowledgebase

Topic Contents

Preterm Labour

Topic Overview

Is this topic for you?

This topic covers preterm labour as it relates to the pregnant woman's problems and care. If you are looking for information about babies who are born too soon, see the topic Premature Infant. Labour and delivery before the end of 20 weeks of pregnancy is called a miscarriage. See the topic Miscarriage for more information.

What is preterm labour?

Preterm labour is the start of labour between 20 and 37 weeks of pregnancy. A full-term pregnancy lasts 37 to 42 weeks. In labour, the uterus contracts to open the cervix. This is the first stage of childbirth.

Preterm labour is also called premature labour.

What are the risks of preterm labour and preterm birth?

The earlier the delivery, the greater the risk for serious problems for the baby. This is because many of the organs—especially the heart and lungs—are not fully grown, or mature. Premature infants born after 32 weeks of pregnancy tend to have less chance of problems than those born earlier.

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 other problems, such as trouble with learning and talking and with moving their body (poor motor skills).

What causes preterm labour?

Preterm labour can be caused by a problem with the baby, the mother, or both. Often the cause is not known.

Preterm labour most often occurs naturally. But 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.

Causes of preterm labour include:

  • The placenta separating early from the uterus. This is called abruptio placenta.
  • Being pregnant with more than one baby, such as twins or triplets.
  • An infection in the mother’s uterus that leads to the start of labour.
  • Problems with the uterus or cervix.
  • Drug or alcohol use during pregnancy.
  • The mother's water (amniotic fluid) breaking before contractions start.

Treatments to help a woman get pregnant have led to more women being pregnant with more than one baby, such as twins or triplets. This has also increased the number of women who have preterm labour and preterm births.

What are the symptoms?

It can be hard to tell when labour starts, especially when it starts early. So watch for these symptoms:

  • Regular contractions for an hour. This means about 4 or more in 20 minutes, or about 8 or more within 1 hour, even after you have had a glass of water and are resting.
  • Leaking or gushing of fluid from your vagina. You may notice that it is pink or reddish.
  • Pain that feels like menstrual cramps, with or without diarrhea.
  • A feeling of pressure in your pelvis or lower belly.
  • A dull ache in your lower back, pelvic area, lower belly, or thighs that does not go away.
  • Not feeling well, including having a fever you can't explain and being overly tired. Your belly may hurt when you press on it.

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 preterm labour contractions do not stop, the cervix begins to open (dilate) or thin (efface). Before or after contractions begin, the amniotic sac that holds the baby may break. This is called a rupture of membranes. It causes a leakage or a gush of amniotic fluid. Rupture of membranes before contractions start is called premature rupture of membranes, or PROM. Before 37 weeks of pregnancy, it is called preterm premature rupture of membranes, or pPROM.

How is preterm labour diagnosed?

If you think you have symptoms of preterm labour, call your doctor or 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 does not find the protein, then you are unlikely to deliver soon. But the test cannot tell for certain if you are about to have a preterm birth.

How is it treated?

If you are in preterm labour, your doctor or certified midwife must weigh the risks of early delivery against the risks of waiting to deliver. Depending on your situation, your doctor or midwife may:

  • Try to delay the birth with medicine. This may or may not work.
  • Use antibiotics to treat or prevent infection. If your amniotic sac has broken early, you have a high risk of infection and must be watched closely.
  • Give you steroid medicine to help prepare your baby’s lungs for birth.
  • Treat any other medical problems causing trouble in pregnancy.
  • Allow the labour to go on because delivery is safer for the mother and baby than letting the pregnancy go on.

Frequently Asked Questions

Learning about preterm labour:

Being diagnosed:

Getting treatment:

Ongoing concerns:

Cause

Preterm labour can be caused by a problem involving the fetus, the mother, or both. Often a combination of several factors is responsible. But in about 1 out of 3 preterm births, the cause is not known.1

Causes of spontaneous preterm labour include:

  • Being pregnant with more than one fetus. Women who are pregnant with more than one fetus have an increased risk of complications—both maternal and fetal—and typically deliver early. See the topic Multiple Pregnancy: Twins or More for more information.
  • Infection, which can trigger uterine contractions and preterm premature rupture of membranes (pPROM). An infection that spreads to the uterus can release substances that make the uterus contract and can cause the amniotic sac to break early (pPROM). Some infections may begin in the vagina, such as bacterial vaginosis (BV), or in the urinary tract, such as a urinary tract infection. Infection of the gums or periodontal disease has also been linked to preterm birth.2
  • Abruptio placenta, which is the early separation of the placenta from the uterus. For more information, see the topic Abruptio Placenta.
  • The use of drugs such as cocaine or methamphetamine.
  • Problems with the uterus or cervix, such as a weak, thin cervix; fibroid growth; or an abnormally shaped uterus.

Symptoms

Preterm labour often starts without obvious symptoms. But you may notice one or more symptoms, including:

  • Menstrual-like cramps, with or without diarrhea.
  • A feeling of pressure in your pelvis or lower abdomen.
  • A persistent, dull ache in your lower back, pelvic area, lower abdomen, or thighs.
  • Changes in your vaginal discharge, which may increase in amount or become pink or reddish.
  • Regular contractions of your uterus for an hour. This means about 4 or more in 20 minutes, or about 8 or more within 1 hour, even after you have had a glass of water and are resting.
  • Not feeling well, including:
    • Unexplained fever.
    • Fatigue.
    • Uterine tenderness.

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, notify your doctor or midwife.

What Happens

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 usually results in few or no serious complications.

Symptoms of preterm labour do not necessarily mean that preterm birth will happen. Your doctor may be able to stop your preterm labour.

If preterm labour contractions do not stop, the cervix may thin (efface) and open (dilate). The amniotic sac may break (rupture), leading to preterm birth. In most cases a woman can deliver vaginally. If the health of the mother or fetus is at risk, a caesarean section may be needed. See the topic Pregnancy for more information.

Premature infant

The more prematurely an infant is born, the greater the risk of medical complications of prematurity. A premature fetus's likelihood of survival increases as the pregnancy advances and as the fetus gains weight. The fetus's stage of development, ability to breathe (lung maturity), and overall health are also important factors for survival. Because of advances in medical care, more premature infants are surviving today than in years past. For more information, see the topic Premature Infant.

What Increases Your Risk

It is hard to predict who is at risk for preterm labour. Some women with risk factors do not have early labour. Others with no known risk factors do have early labour.

Preterm labour and preterm birth

Most premature births happen after naturally occurring, or spontaneous, preterm labour (as opposed to a medically necessary preterm birth, when the baby must be delivered as quickly as possible to prevent harm to mother or baby).

Experts say that spontaneous preterm labour is often the result of a combination of factors. Some of the most common medical risk factors for a spontaneous preterm birth are:

  • Pregnancy with twins, triplets, or more. (Use of assisted reproductive technology (ART) or superovulation increases the risk of multiple pregnancy, which carries a high risk of premature birth and resulting medical complications.3)
  • In vitro fertilization (IVF), a type of ART. IVF twins may be born earlier than naturally conceived twins.3
  • A past preterm delivery.
  • Vaginal bleeding in the second trimester.
  • Infection in the urinary or reproductive tract, including the vagina.
  • Age younger than 18 years.
  • Mother's low body weight for height (body mass index).
  • Cigarette smoking during pregnancy.
  • Frequent contractions.

Other factors that may increase your risk for premature labour include:

When To Call a Doctor

Preterm labour can be hard to recognize. Get the earliest possible medical care for preterm labour by calling your doctor or your midwife about signs of possible preterm labour.

Any time during your pregnancy

Call your doctor or your midwife if you have:

  • An increase or gush of fluid from your vagina. It is possible to mistake a leak of amniotic fluid for a problem with bladder control or excess cervical mucus.
  • Bleeding or spotting from your vagina.
  • Painful or frequent urination or urine that is cloudy, foul-smelling, or bloody.

Between 20 and 37 weeks of your pregnancy

Call your doctor, your midwife, or the labour and delivery unit of your local hospital if:

  • You have had regular contractions for an hour. This means about 4 or more in 20 minutes, or about 8 or more within 1 hour, even after you have had a glass of water and are resting.
  • You have unexplained low back pain or pelvic pressure.
  • You have uterine tenderness, unexplained fever, or weakness (possible symptoms of infection).
  • You have intestinal cramping with or without diarrhea.
  • The baby has stopped moving or is moving much less than normal. See fetal movement counting for information on how to check your baby's activity.

Watchful Waiting

If you are having painless or mild contractions that are irregular or more than 15 minutes apart:

  • Stop what you are doing.
  • Empty your bladder.
  • Drink 2 to 3 glasses of water or juice (too little body fluid can cause contractions).
  • Lie down on your left side for at least an hour, and keep track of how often you have contractions.

Call your doctor or midwife if you have had regular contractions for an hour. This means about 4 or more in 20 minutes, or about 8 or more within 1 hour, even after you have had a glass of water and are resting.

If your contractions stop, they were probably Braxton Hicks contractions, which are harmless and normal. Braxton Hicks contractions are often irregularly timed and uncomfortable rather than painful.

Who To See

If you are in premature labour, you may be seen by:

You may continue to see your registered midwife, who will consult with one of the doctors listed above.

If it appears that your labour cannot be stopped, you may also see a neonatologist, a doctor who specializes in the intensive care of infants.

To prepare for your appointment, see the topic Making the Most of Your Appointment.

Examinations and Tests

If you have symptoms of preterm labour, both you and your fetus will be examined and monitored.

For the mother

You will be examined for tenderness in your uterus. Your temperature, pulse, and rate of breathing will be checked. Depending on the nature of your symptoms, you may have one or more examinations or tests, including:

  • A vaginal examination, to find out whether the contractions have begun to open (dilate) or thin (efface) your cervix.
  • A vaginal smear, which may be collected to check for:
    • Infection. Disease-causing organisms in the vagina can cause uterine infection, triggering preterm labour and serious infection in the newborn.
    • Amniotic fluid, which shows that the amniotic sac has broken.
    • Fetal fibronectin, which does not tell for sure if you are having preterm labour. When the test is negative, it is unlikely that you are having preterm labour. But even if the test is positive, it does not mean for sure that you are having preterm labour. This test is not useful for actually predicting preterm labour and is not used in all labour and delivery units. It is done before a pelvic examination to reduce the risk of a false-positive result.

Other tests that may be done to check for infection include:

If you have an infection, you may be treated with antibiotics.

For the fetus

  • Your fetus's health is checked using electronic fetal heart monitoring, which records fetal heartbeats. Fetal monitoring also checks, records, and times the mother's contractions and shows how the fetus's heart rate reacts to each uterine contraction.
  • A fetal ultrasound test may be used to:
    • Find out whether more than one fetus is in the uterus.
    • Estimate the age, weight, and position of the fetus.
    • Locate and check the condition of the placenta.
    • Check the length of the cervix. A short cervix is a sign that preterm labour may be likely to happen.
  • Amniocentesis is sometimes used to take amniotic fluid from the uterus. This test is most commonly used to test the amniotic fluid for:
    • Signs of infection.
    • Substances that show whether the fetus can breathe without assistance, in case of premature birth.

All of this information can help you and your doctor or midwife decide whether to treat premature labour and delay the birth or allow premature labour to continue and manage any complications that might occur.

Treatment Overview

Treatment to slow your preterm labour contractions may be used if:

  • You are between 23 and 34 completed weeks of pregnancy.
  • You are having regular contractions. This means about 4 or more in 20 minutes, or about 8 or more within 1 hour, even after you have had a glass of water and are resting.
  • Your cervix has opened (dilated) to more than 2 centimetres and has begun to thin (efface).

Preterm labour is not always treated. When a pregnancy is nearing term (about 37 or more weeks), or when the mother or her fetus has a serious medical problem, preterm labour is usually allowed to continue until delivery.

When deciding on the amount and type of treatment, your doctor or midwife will think about:

  • Your baby's weight and age. Ideally, preterm labour is delayed until a baby is mature enough that complications after birth are unlikely. The closer the baby is to full term and the more a baby weighs, the better the baby's chances of surviving and avoiding complications.
  • Your health. Very high blood pressure, severe pre-eclampsia, HELLP syndrome, chronic disease, infection, or heavy bleeding can make it necessary to deliver immediately rather than try to delay a birth.
  • Your baby's health. Signs of fetal distress or illness can make it necessary to deliver immediately rather than try to delay a birth.
  • Whether your amniotic sac has ruptured (preterm premature rupture of membranes, or pPROM).
  • The stage of your labour and its rate of progression. For example, when your cervix is well effaced (thinned) and dilated (opened) beyond 4 centimetres, tocolytic medicine to slow labour is less likely to be effective.
  • The distance to a neonatal intensive care unit (NICU). If there is a good chance that you could be transferred to a hospital with a NICU before the birth, your doctor may try to slow labour. If the baby is born before you are transferred, he or she may be transferred after birth if necessary.
  • The benefit of the tocolytic medicines used to delay labour versus their risks to you and your baby.

If you are treated for preterm labour

Preterm labour is usually treated in the hospital, in the labour and delivery area. Whether your amniotic membranes have ruptured before contractions start (preterm premature rupture of membranes, or pPROM) or after contractions have begun (spontaneous rupture of membranes, or SROM), you will be admitted directly to the labour and delivery unit. If rupture of membranes has not occurred, you will be observed for at least an hour or two to see whether your contractions continue and your cervix changes (opens and thins).

  • If your cervix does not 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.

If you are admitted to the labour and delivery unit, your doctor or midwife may choose to:

  • Use medicine to try to slow or stop the contractions, to prevent the cervix from opening wider (dilating) or becoming thinner (effacing). Short-term treatment with tocolytic medicine is the current treatment. If effective, tocolytics may delay birth for more than 48 hours.5
  • Treat or prevent infection with antibiotics.
  • Help the fetus's lungs mature quickly with antenatal corticosteroids (given to you). These medicines take 24 to 48 hours to benefit the fetus.

There is no proof that long-term bedrest lowers the risk of preterm delivery.6 But your doctor may advise you to take it easy and try to rest as much as possible. Studies have shown that strict bedrest for 3 days or more may increase your risk of getting a blood clot in the legs or lungs.7 Strict bedrest is no longer used to prevent preterm labour. But if your doctor has recommended expectant management with some bedrest (partial bed rest), remember to flex your feet, stretch, and move your legs as much as possible.

Cervical cerclage is the placement of stitches in the cervix to hold it closed. Cerclage is meant to stop the cervix from opening early, which could lead to miscarriage or preterm birth. It is not used to treat preterm labour. But for a woman who has had a preterm birth in the past because her cervix did not stay closed, cervical cerclage may prevent another preterm birth.1

Prevention

Even if you have a healthy pregnancy, you may go into preterm labour. It is hard to prevent preterm labour because it is usually not anticipated. Also, it is often due to causes that are not completely understood. But building some healthy pregnancy habits may help prevent preterm labour and will optimize your fetus's health and ability to thrive, whether at full term or preterm.

Being pregnant with twins, triplets, or more puts you at high risk for preterm labour and infant complications. If you are planning to use assisted reproductive technology or superovulation to conceive, talk to your doctor about reducing your risk of conceiving more than one baby. For more information, see the topics Fertility Problems and Multiple Pregnancy: Twins or More.

If contractions start

Contractions are a normal part of all pregnancies. Most contractions do not thin and open the cervix. Rather, they are simply a brief stimulation of the uterine muscle. This can happen when your fetus is moving a lot, when your bladder or bowel is full, or when you are dehydrated. These non-labour contractions are irregularly timed and uncomfortable rather than painful.

Preterm labour contractions tend to be regularly timed, becoming more frequent, painful, and prolonged (30 to 60 seconds) as they progress. You may also notice low back pain, thigh pain, or increased vaginal discharge or bleeding.

If you are less than 37 weeks pregnant and your uterus is contracting more than usual (about 4 or more in 20 minutes or about 8 or more within 1 hour), the following steps may stop your contractions:

  • Drink 2 or 3 glasses of water or juice (not having enough liquids can cause contractions).
  • Stop what you are doing, empty your bladder, and lie down on your left side for at least an hour.

If your symptoms get worse during the hour, call your doctor or midwife or go to the hospital.

If you are at risk for preterm labour

If you have had a spontaneous preterm birth before, you are probably at high risk for another preterm labour. This might make you a candidate for weekly progesterone injections for preventing preterm labour and delivery. No fetal or newborn harm has been observed, though ongoing research is needed to rule out long-term side effects.8

You may be able to help prevent preterm labour if you are at risk (see the What Increases Your Risk section of this topic). Avoid activities that can start contractions, such as smoking.

Home Treatment

Symptoms of preterm labour are warning signs. They do not necessarily mean that you will have a preterm birth.

If you are less than 37 weeks pregnant and your uterus is contracting more than usual, the following steps may stop your contractions:

  • Drink 2 or 3 glasses of water or juice. Not having enough liquids can cause contractions.
  • Stop what you are doing, empty your bladder, and lie down on your left side for at least 1 hour.
  • Try to remember what you were doing when the symptoms started so that you can avoid starting the contractions again later.
  • If your contractions get worse during the hour, call your doctor or midwife, or go to the hospital.

Although stress is not considered 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.

If you have already been treated for preterm labour

If your contractions stop, you may be sent home from the hospital. Before you are discharged, you should know:

  • The symptoms of preterm labour, including lower pelvic ache or backache, pressure, or cramps.
  • What to do if preterm labour starts again, including drinking fluids, resting, and calling your doctor if symptoms don't improve in 1 hour.
  • When to call your doctor or midwife. See the When to Call a Doctor section of this topic.

Medications

If your contractions are causing changes in your cervix (preterm labour), or you have signs of infection or preterm premature rupture of membranes (pPROM), you may be treated with one or more medicines, including:

  • Antibiotics, to prevent or treat infection. Antibiotic treatment does not always get rid of infection. But it often prevents infection when the amniotic sac has ruptured (pPROM) and can also delay delivery after pPROM.1
  • Medicines (antenatal corticosteroids) to speed up fetal lung development if birth is anticipated between the 24th and 34th weeks of pregnancy.
  • Tocolytic medicines, to slow down contractions and try to delay labour for a day or two.

Delaying labour even for a short time can allow you to be:

  • Transported to a medical centre that has a neonatal intensive care unit (NICU).
  • Given antenatal corticosteroids, which take a minimum of 48 hours to fully benefit a fetus's lungs. Even 24 hours provides some benefit.

Medication Choices

Antibiotic medicine is chosen by your doctor or midwife based on the type of infection present.

Antenatal corticosteroids (betamethasone or dexamethasone) help prepare the fetus's lungs for preterm birth.

Tocolytic medicines that are used to stop preterm labour include:

What To Think About

If you have had a spontaneous preterm birth in the past, you are probably at high risk for another preterm labour. This might make you a possible candidate for weekly progesterone for preventing preterm labour and delivery. No fetal or newborn harm has been observed, though long-term research has not been done to rule out long-term side effects.8

A single course of antenatal corticosteroid treatment, used to prepare the fetus's lungs for birth, is considered to be the least risky, most effective treatment available for avoiding the most common preterm fetal complications at birth. It is standard procedure to give corticosteroid injections to most women before preterm birth, especially for pregnancies at 24 to 34 weeks of gestation.

Before using tocolytics, your doctor will consider your and your fetus's health, how far your labour has progressed, whether your membranes have ruptured, and whether you have an infection. 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).

Surgery

Surgery is rarely done to prevent preterm birth.

Cervical cerclage is the placement of stitches in the cervix to hold it closed during pregnancy. It is meant to stop an incompetent cervix from opening early (which could lead to miscarriage or preterm birth).

Surgery Choices

Cervical cerclage (placement of stitches in the cervix to hold it closed, with the intention of preventing preterm labour and delivery)

What To Think About

Cerclage has helped some high-risk pregnancies last longer, but it also has risks. It can cause infection or miscarriage. For a woman who has had a preterm birth in the past because her cervix did not stay closed, cervical cerclage may prevent another preterm birth.1

Other Treatment

There are no other treatment choices for preterm labour.

Other Places To Get Help

Organization

Society of Obstetricians and Gynaecologists of Canada (SOGC)
780 Echo Drive
Ottawa, ON  K1S 5R7
Phone: 1-800-561-2416
(613) 730-4192
Fax: (613) 730-4314
Email: helpdesk@sogc.com
Web Address: www.sogc.org
 

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.


References

Citations

  1. Haas DM (2010). Preterm birth, search date June 2009. Online version of BMJ Clinical Evidence: http://www.clinicalevidence.com.
  2. 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.
  3. 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.
  4. Samson SA, et al. (2005). The effect of loop electrosurgical excision procedure on future pregnancy outcomes. Obstetrics and Gynecology, 105(2): 325–332.
  5. American Academy of Pediatrics and American College of Obstetricians and Gynecologists (2002). Obstetric and medical complications. In Guidelines for Perinatal Care, 5th ed., pp. 163–185. Washington, DC: American Academy of Pediatrics, American College of Obstetricians and Gynecologists.
  6. American College of Obstetricians and Gynecologists (2003, reaffirmed 2008). Management of preterm labor. ACOG Practice Bulletin No. 43. Obstetrics and Gynecology, 101(5): 1039–1047.
  7. Cunningham FG, et al., eds. (2010). Preterm birth. In Williams Obstetrics, 23rd ed., pp. 804–831. New York: McGraw-Hill.
  8. 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.
  • 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.

Credits

By Healthwise Staff
Primary Medical Reviewer Sarah Marshall, MD - Family Medicine
Primary Medical Reviewer Brian D. O'Brien, MD - Internal Medicine
Specialist Medical Reviewer William Gilbert, MD - Maternal and Fetal Medicine
Last Revised March 21, 2011

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.