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premature labour

Alternative Names
preterm labour

In most pregnancies, labour starts at about 40 weeks. Labour that starts before the end of the 37th week is considered preterm. Preterm labour can lead to preterm birth. Every year over 6% of pregnancies in Australia end in preterm birth. It is also the single largest cause of death and illness for newborn babies.

What is going on in the body?
Labour may start with regular contractions of the uterus. The cervix thins out and dilates, or opens up, so the baby can enter the birth canal. Sometimes labour begins earlier than it should. If preterm labour is caught quickly, delivery may often be postponed. This gives the baby extra time to grow and mature. Growth and development in the last part of pregnancy are critical to the baby's health. A baby born too early is at risk.

If a preterm delivery seems likely, the doctor will try to determine if the baby's lungs are mature enough to survive outside the uterus. If the lungs are not mature enough, the baby may develop respiratory distress syndrome. This is the most common cause of death in preterm babies.

What are the signs and symptoms of the condition?
Sometimes the signs of preterm labour are fairly easy to detect. But sometimes they are mild and harder to notice. The mother should call the doctor right away if she has any of these common signs of preterm labour:
  • change in the type or amount of vaginal discharge
  • pelvic or lower abdominal pressure
  • constant low, dull backache
  • mild abdominal cramps, with or without diarrhoea
  • regular contractions of the uterus, often painless cramping like a menstrual period
  • ruptured membranes, with amniotic fluid leaking from the vagina
What are the causes and risks of the condition?
In 50 to 60% of preterm labours, the cause is not known. The factors known to cause preterm labour can be divided into major and minor ones.

Major factors:
  • history of preterm labour or birth
  • two previous second-trimester abortions
  • multiple pregnancy
  • defects in the uterus such as an incompetent cervix, fibroids, or double uterus
  • excess amniotic fluid
  • abdominal surgery during pregnancy
  • irritable uterus
  • birth defects in the foetus
Minor factors:
  • one previous second-trimester abortion
  • three previous first-trimester elective abortions
  • bleeding after 12 weeks
  • weight less than 45 kg
  • any illness with high fever (39+ degrees Celsius)
  • smoking more than 10 cigarettes a day
  • water breaking (ruptured membranes)
  • high blood pressure
  • chronic illness, such as diabetes
What can be done to prevent the condition?
Because the exact cause is uncertain, prevention is very difficult. The current strategy is to identify in advance the women who are most at risk for preterm labour. Intensive education of women in this high-risk group is important. A wide mixture of social, physical, and pregnancy factors can contribute to preterm labour. Preterm labour can happen to anyone, but it is more likely in women who do not get antenatal care. So antenatal care is considered an important means of preventing preterm labour and birth.

How is the condition diagnosed?
A woman who notices any of the signs of premature labour should see the doctor. The cervix is checked immediately to see whether it has begun to change. An ultrasound may be performed to check cervical length

foetal monitoring is used to record the heartbeat of the foetus and the contractions of the uterus. Pregnancy ultrasound may also be used to estimate the size and age of the baby and to see how it is lying in the uterus.

What are the long-term effects of the condition?
Preterm babies, also called premature babies or premies, tend to grow more slowly than normal. They may have learning and behavioural problems, and problems with their eyes and ears and with breathing.

What are the risks to others?
Preterm labour and the possibility of a preterm baby can create a major emotional and financial crisis. The mother, father, and baby will need a lot of support. A hospital social worker or chaplain may be able to help the parents cope with the situation.

What are the treatments for the condition?
If there is no sign that the mother or foetus is in danger from infection, bleeding, or other problems, the doctor may try to stop preterm labour. The goal is to allow the foetus more time to grow and mature. Among the many ways to do this are medications that can stop or suppress uterine contractions. Labour should not be stopped if there is foetal distress, poorly controlled diabetes, severe high blood pressure, uterine infection, or bleeding.

What are the side effects of the treatments?
A number of medications can be used to stop or slow preterm labour. It's not always clear which is the best one to use. The medications are usually injected. As with all medications, they can have side effects, and each woman responds differently. Possible side effects include:
  • fast pulse
  • chest pressure or discomfort
  • dizziness
  • headache
  • feeling of warmth
  • shaky or nervous feeling
What happens after treatment for the condition?
If labour is successfully stopped, the mother may be able to go home. She would then need to continue to monitor herself. This can be done by lying down and gently feeling the entire surface of the lower abdomen with her fingertips.

How is the condition monitored?
In the hospital, ultrasound and Foetal monitoring are used. Mobile monitoring is available for use at home.

Author: Dr. Karen Wolfe, MBBS, MA
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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