Preterm Labour

Key Messages

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These are the main health messages that should be conveyed to all future and new parents. They have been written in the second person and at a reading level appropriate for the general public so that they can be shared with them directly. They are based on a consensus founded in scientific research and professional practice. Clicking an underlined word or group of words in the text will redirect you to the section in Supporting Evidence that deals with that topic.

Preterm labour can lead to preterm birth.

Labour is the natural process where the uterus contracts causing the cervix to thin out and open so your baby can be born. This normally happens between 37 and 42 weeks of your pregnancy. Preterm labour is labour that starts before the 37th week of pregnancy. Your due date is the date that you are estimated to be 40 weeks pregnant based on your last menstrual period and/or ultrasound.

Preterm labour can lead to preterm birth. Preterm birth is when the baby is born between 20 and 37 weeks of pregnancy. Premature babies need to be cared for in special units in the hospital. Babies may have to stay in the hospital for a few weeks to a few months until they are strong enough to go home with their families. Premature babies are at risk for medical problems after they are born. Some premature babies are too small, too immature, or too sick to survive.

Be alert for signs of preterm labour especially if you are at risk.

You may have an increased risk of having preterm labour if:

  • You had preterm labour or a preterm baby in the past.
  • You had several miscarriages.
  • You had a suture placed in your cervix during the pregnancy or have been told you have a short cervix.
  • You have a urinary tract infection or certain sexually-transmitted infections.
  • Your water breaks before the 37th week. This is called premature rupture of the membranes.
  • You are pregnant with more than one baby.
  • You were underweight before getting pregnant or you are not gaining enough weight during the pregnancy.
  • You smoke or take illegal drugs during the pregnancy.
  • You are under the age of 18 or over the age of 35.
  • You have a lot of stress or violence in your life.
  • You do very hard work at your job or home.
  • You work shifts; you stand for long periods of time at your work; you work in temperature extremes (like a bakery).

It is important to get immediate medical attention if you think you may be in preterm labour.

Even if you don’t have any risk factors for preterm labour, you should see your health care provider if you have any of the following signs  before 37 weeks of pregnancy:

  • You have cramps or contractions in your uterus that are happening more than normal for you or more than four in an hour. Preterm contractions may not be painful in preterm labour.
  • The cramps or contractions do not go away or are not getting better no matter what you do.
  • You have cramps or contractions that are becoming more uncomfortable or painful.
  • You have bleeding or an increase in discharge from your vagina.
  • You think your bag of water has broken, or you feel a gush of fluid from your vagina, or your underwear is more wet than normal.
  • You have a low backache that is getting more uncomfortable, pressure in your bowels like you want to have a bowel movement, or pressure in your pelvic area or vagina.
  • You just don’t feel right.

You must go to the hospital or be seen by your health care provider to be assessed. It is always better to go and be assessed than to stay home and worry.

If you have questions and are not able to speak with your health care provider, call Telehealth Ontario at 1-866-797-0000 to speak to a Registered Nurse. This service is available in English and French with translators available for other languages. It is available 24 hours a day and seven days a week. If you have a midwife, you can page your midwife or her colleagues anytime using the number given to you when you started midwifery care.

If you have a high risk of preterm birth or have signs that you might be in preterm labour, your health care provider will assess you and may offer treatments to reduce the chance of having a preterm birth.

Assessments and treatments for preterm labour may include:

  • Ultrasound to see if the length of the cervix is shortening.
  • Speculum exam to examine the cervix, check for bleeding, and collect cells from your cervix with a swab to assess your risk of going into preterm labour and/or to see if you have an infection.
  • Medications such as:
    • Steroids to help the baby’s lungs develop in case the baby will be born early.
    • Antibiotics if you have an infection or to prevent infection.
    • Medications to attempt to slow down labour.
  • Being admitted to the hospital to rest and be monitored more closely.
  • Being transferred to or staying at a level two or level three hospital until your baby is born. Level two and level three hospitals have experience caring for women with preterm labour and special nurseries for preterm babies.

Your health care provider may suggest that you:

  • Decrease your sexual activity and stop having sex and orgasms. Sexual intercourse can sometimes trigger uterine contractions.
  • Stop work, stay at home, decrease your activity, and spend more time resting.

Sometimes medical care does not prevent a premature birth. In this situation, your baby would be cared for in a special-care nursery until your baby is ready to go home.

Learn more about preterm labour

You can found out more about preterm labour from the following resources. More suggestions can be found in the Resources and Links section.

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Supporting Evidence

The supporting evidence is written in third person and is aimed at prenatal education providers. It is not intended to be shared directly with new and expectant families; it is meant to provide the background information and evidence for the key messages.

About Preterm Labour

Defining preterm labour

Labour is the normal physiologic process by which the uterus contracts causing the cervix to efface and dilate. The contracting uterus also assists the fetus in descending into the pelvis and with maternal expulsive effort, the fetus is born. Labour normally occurs between weeks 37 and 42 of pregnancy. Labour that begins after 20 weeks and before 37 weeks is termed preterm labour. 1,2,3,4

The estimated date of birth (EDB) or due date is given for 40 weeks of pregnancy and is calculated from a woman’s last menstrual period or by ultrasound. It is important for women to have an accurate determination of their due date to guide appropriate obstetrical care such as timing and interpretations of investigations and determining the period of viability in a preterm labour situation. It is recommended that women have an ultrasound in the first trimester for gestational dating since it is the most accurate method to determine the due date.5

Complications of preterm labour

Preterm labour is one of the major causes of preterm birth.6 Premature infants must be cared for in a tertiary care centre with a Level 3 neonatal intensive care unit (NICU). In Ontario, there are eight of these facilities that specialize in the care of extremely premature infants (i.e., 28 weeks and younger) and very premature infants (i.e., 32 weeks and younger). Infants who are born after 32 weeks and weighing 1500 grams or more can be cared for in a Level two NICU.1

Premature infants may have to stay in the hospital anywhere from a few weeks to a few months depending on their gestational age at birth, their health status, and their progress and development. Prematurity puts them at risk for developing medical complications during their hospitalization and later during their childhood.1,4,6,7

The mortality rate of premature infants is dependent on the gestation, pregnancy and birth events, weight and acquired morbidities. Infants born before the age of viability (i.e., before 23 weeks) are considered too small and immature to survive.6

International, national and provincial statistics

Since there are no accurate measurements for preterm labour, statistics report on the outcome of preterm labour (i.e., preterm birth).

Preterm birth is considered a global health problem. In countries with lower incomes, there is an average preterm birth rate of 12 percent, and in countries with higher incomes the rate is approximately 9 percent. The United States has the sixth-highest preterm birth rate in the world.1,5,7

In Canada, the premature birth rate remained fairly constant at 7.9 percent from 2006 – 2011.8,9 For the year 2011 in Ontario, approximately 8.1 percent of infants were born prematurely; this translates to 1 in 12 babies.8,9,10

Certain factors have been associated with changes in premature birth rates including the following:1,4,6,8

  • People with lower socioeconomic status have a higher rate of preterm birth.
  • Increased number of multiple pregnancies through assisted reproductive technologies.
  • Increased maternal age.
  • Changes in maternal health status.
  • Advances in antepartum fetal surveillance.
  • Advances in technology and increased use of obstetrical interventions.

Preterm Labour Causes and Signs

Risk factors for preterm labour

Many factors have been associated with increased risk of experiencing preterm labour and/or preterm birth. Some of these factors are modifiable while others are not.2,3,4,11,12,13,14

These risk factors include:

  • Previous preterm birth.
  • Previous history of preterm labour.
  • Preterm rupture of the membranes.
  • Multiple pregnancy.
  • Perinatal infections such as chorioamnionitis or a urinary tract infection.
  • Some sexually-transmitted infections such as Chlamydia, gonorrhea, or bacterial vaginosis.
  • Periodontal infections.
  • Maternal age, with the highest risk being less than 18 years of age or greater than 35 years of age.
  • Low or high BMI.
  • Poor weight gain in pregnancy.
  • Poor nutrition in pregnancy.
  • Poor health status.
  • Type of work, for example, heavy lifting, increased job stress, standing for long periods of time, shift work, working in temperature extremes.
  • Stressful living situations including domestic abuse or violence.
  • Tobacco use.
  • Illegal drug use.

In some situations, no reason can be found to explain why a woman went into preterm labour.2,4

It is important to note that not all women experiencing preterm labour will have a preterm birth.2,4 Additionally, not all preterm births are due to preterm labour. Sometimes the preterm birth will be a result of a medically-indicated delivery for maternal or fetal health reasons.6

Signs of preterm labour

It is important that all women learn the signs of preterm labour and seek medical care without delay if they have any signs of preterm labour.1,2,3,4

The signs of preterm labour include:1,2,3,4

  • Menstrual-like cramps or uterine contractions beyond the normal amount for each individual woman, or more than four per hour.
  • Cramps or contractions that are painful or becoming more painful.
  • Cramps or contractions that are persisting no matter what the woman is doing.
  • Bleeding from the vagina or an increase in vaginal discharge.
  • Rupture of the amniotic sac, a gush of fluid from the vagina, or wet underwear or pants.
  • Backache, rectal pressure, or vaginal pressure.
  • A general sense of not feeling well.

It is important to note that sometimes contractions can be painless when a woman is in preterm labour.

Management of Preterm Labour

Care of women in preterm labour

If preterm labour cannot be prevented by modifying or reducing the risk factors, a woman’s health care provider may be able to delay or halt the process and prevent or at least reduce the chance of having a preterm birth.2,3,4

Diagnostic tests and treatment

Admission to the hospital may be required in some circumstances for close monitoring or if preterm birth is likely. There are tests and treatments associated with diagnosing and treating preterm labour, including the following:2,3,4,14,15,16

  • Serial ultrasounds to assess the cervical length and determine the need for further treatments, including possible cervical cerclage (temporary surgical closure of the cervix) if less than 24 weeks.
  • Fetal fibronectin test to determine the presence of the protein fetal fibronectin (fFN) which can indicate a greater chance of preterm labour.
  • Urine, cervical, and vaginal samples to assess for infections.
  • Administration of steroids to stimulate the production of surfactant in the fetal lungs and assist with fetal lung maturity. These drugs are often given if preterm birth  is a possibility.
  • Administration of other medications to try to slow or stop the progress of the preterm labour. This can buy time to allow the steroids to take effect.
  • Administration of antibiotics for infection or prophylaxis.

Lifestyle modifications

Some lifestyle modifications have been widely used to reduce the chance that a woman may experience preterm labour and also prevent aggravating the condition.2 Since medical research in this area is ongoing, researchers are determining the effectiveness as well as the risks and benefits to women adopting these lifestyle modifications.15,16 An individualized approach for care should be planned for each woman.15,16

Some women will be advised to decrease or cease sexual intercourse since nipple and genital stimulation may cause oxytocin to be released causing contractions. In addition, prostaglandins released from the cervix and semen may cause the cervix to ripen and may cause the women to go into labour.15,17

It may be recommended that women decrease their working hours, work from home, and avoid commuting. Others may have to stop working altogether depending on the nature of the job, the amount of stress generated by the job, and their medical conditions.11

Some physicians may advise that women at risk for preterm birth go on bed rest, where the woman spends most of the day either sitting or lying down. Some women will be admitted to a hospital for closer monitoring or to increase rest.15,16,18

The concept of bed rest has been challenged in its effectiveness, risks, and benefits; however it remains a fairly prevalent recommendation for the prevention and/or management of preterm labour.15,16,18

Sometimes, despite all the medical care given, labour cannot safely or effectively be stopped, and the birth of a preterm infant is expected.15,16

Preventing preterm labour and preterm birth

Although not all preterm births can be prevented, there are some clear, evidence-based approaches that are universal such as:2,3,4,14,16

  • Advising women to seek prenatal care early in the pregnancy.
  • Encouraging women to reduce or stop smoking and to stop taking illegal drugs.
  • Encouraging women to identify and manage stress in their lives. Stress may be relationship, domestic, or work-related.
  • Counselling women about the risks of STIs and practicing safe sex.
  • Early identification and treatment of infections, particularly urinary tract infections.
  • Encouraging women to eat a healthy diet during pregnancy and maintain an adequate weight gain.
  • Advising women to have good oral hygiene and to visit the dentist during the pregnancy.
  • Advising all pregnant women to learn about the signs and symptoms of preterm labour.
  • Advising all pregnant women seek medical care if experiencing any signs or symptoms of preterm labour.


When to refer

Consider referring women to outside resources if there is a concern about their risk for preterm labour, ability to recognize signs and symptoms, or challenges with management of the pregnancy, including:

  • Women who have had preterm labour or a previous preterm birth.
  • Women currently at risk for preterm labour.
  • Women who note any of the signs and/symptoms of preterm labour.
  • Women who identify they may be at risk for preterm labour.
  • Women treated for preterm labour at home or in a hospital.

Where to refer

Women who require further assistance beyond prenatal education services should be encouraged to contact one of the following resources:

  • Hospital (especially if experiencing any signs or symptoms of preterm labour).
  • Their  health care provider (obstetrician, family physician, Nurse Practitioner or midwife)
  • Their local public health department.
  • Service Canada (Employment Insurance).
  • Hospital-based or community-based mental health/stress management clinics.

Women who are experiencing any signs or symptoms of preterm labour should go to the hospital for an assessment right away.

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Resources & Links

Please note this is not an exhaustive list of available resources, nor should any of these resources be used in place of seeking professional advice. The resources cited throughout this resource are not necessarily endorsed by the Best Start Resource Centre or the Government of Ontario. When in doubt, professionals should contact the organization responsible for issuing a specific recommendation/practice guideline.

Professional Guidelines

Professional Associations




  • Telehealth Ontario 1-866-797-0000

Client Resources and Handouts


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  1. World Health Organization. (WHO) (2014). Preterm Birth Fact Sheet: number 363. Retrieved from
  2. Best Start Resource Centre. (2004). Preterm labour: Signs and symptoms. Retrieved from
  3. Region of Peel. (2014). Health during pregnancy. Retrieved from
  4. The Source for Women’s Health: Premature/Preterm Birth. Retrieved from
  5. Society of Obstetricians and Gynaecologists of Canada. (2014). Determination of Gestational Age by Ultrasound: Clinical Practice Guidelines: Fetal health surveillance: Antepartum and intrapartum consensus guideline. Journal of Obstetrics and Gynaecology Canada, 303, S171-S181. Retrieved from
  6. Belizán, J., Hofmey, J., Bueken, P., & Salaria, N. (2013). Preterm birth, an unresolved issue Reproductive Health, 10(58). doi:10.1186/1742-4755-10-58
  7. Blencowe, H., Cousens, S., Oestergaard, M., Chou, D., Moller, A., Narwal, R., Adler, A., Garcia, C., Rohde, S., Say, L., & Lawn, J. (2012). National, regional, and worldwide estimates of preterm birth rates in the year 2010 with time trends since 1990 for selected countries: a systematic analysis and implications. Lancet, 379(9832), 2162-2172. doi:
  8. Public Health Agency of Canada (2013). Perinatal Health Indicators for Canada. A report from the Canadian Perinatal Surveillance System. Retrieved from
  9. Canadian Institute for Health Information. (2012). Highlights of 2010 – 2011 selected indicators describing the birthing process in Canada. Retrieved from
  10. Better Outcomes Registry and Network (BORN) Ontario. (2012). Perinatal Health Indicators for Ontario 2012 Retrieved from
  11. Mozurkewich, E., Luke, B., Avni, M., & Wolf, F. (2000). Working conditions and adverse pregnancy outcome: A meta-analysis. Obstetrics & Gynecology, 95(4), 623-35. DOI:10.1016/S0029-7844(99)00598-0
  12. Cnattingius, S., Villamor, E., Johansson, S., Edstedt Bonamy, A., Persson, M., Wikström, A., & Granath, F. (2013). Maternal obesity and risk of preterm delivery. Journal of the American Medical Association, 309(22), 2362-2370. doi:10.1001/jama.2013.6295
  13. Huck, O., Tennenbaum, H., & Davideau, J. (2011). Relationship between periodontal diseases and preterm birth: Recent epidemiological and biological data. Journal of Pregnancy, 2011. doi: 10.1155/2011/164654
  14. Saini, R., Saini, S., & Saini, S.R. (2010). Periodontitis: A risk for delivery of premature labor and low-birth-weight infants. Journal of Natural Science Biology and Medicine, 1(1), 40–42. Retrieved from
  15. Society of Obstetricians and Gynaecologists of Canada. (2007). Fetal health surveillance: Antepartum and intrapartum consensus guideline. Journal of Obstetrics and Gynaecology Canada, 197, S1-S60. Retrieved from
  16. Piso, B., Zechmeister-Koss, I., & Winkler R. (2014). Antenatal interventions to reduce preterm birth: an overview of Cochrane systematic reviews. Biomedical Central Research Notes, 7(265). doi:10.1186/1756-0500-7-265
  17. Jones, C., Chan, C., & Farine, D. (2011). Sex in pregnancy. Canadian Medical Association Journal,187(7), 815-818. Retrieved from
  18. Sprague, A. O’Brien, B., & Newburn-Cook, C. (2008). Bed rest and activity restriction for women at risk for preterm birth: A survey of Canadian prenatal care providers. Journal of Obstetrics and Gynaecology Canada, 30(4), 317-326. Retrieved from

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