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 placenta abruptio.
- A blood pressure problem in pregnancy called pre-eclampsia.
- 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:
- Contractions of your uterus, about 4 in 20 minutes or 8 every hour, that don't go away.1 These contractions may make your belly feel firm.
- 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 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 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 must weigh the risks of early delivery against the risks of waiting to deliver. Depending on your situation, your doctor 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. This treatment has some risks, but it can improve your baby’s chances of surviving a premature birth between 24 and 34 weeks of pregnancy.2
- 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:
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| Author: | Kathe Gallagher, MSW Carrie Henley | Last Updated: April 10, 2007 |
| Medical Review: | Joy Melnikow, MD, MPH - Family Medicine Anne C. Poinier, MD - Internal Medicine Gregory A L Davies, MD, FRCSC, FACOG - Maternal-Fetal Medicine William Gilbert, MD - Perinatology | |
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