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Preterm Labour Risks
Answers to many common questions
Very few babies are born on their due date, at 40 weeks of pregnancy. Most are delivered within two weeks before or after this date (at 38 to 42 weeks of pregnancy). The time when there is concern about a baby arriving too early is if birth occurs at less than 37 weeks of pregnancy. This is called a preterm birth and in Canada, 6 per cent of births fall into this category.
This rate has not changed in over 20 years. Although there is no medical treatment available to prevent preterm birth once preterm labour (PTL) begins, there are ways to improve the baby's health and chance of survival. If parents to be understand the factors that increase the risk for PTL and the warning signs of PTL, it is hoped more babies will be born closer to their due dates or with specialized medical help available.
Delivering a baby preterm carries with it greater risks for the baby's life and health. Medical care for preterm infants has improved so much that nowadays, half of all babies born at 24 weeks of pregnancy (16 weeks early!) will survive. At 25 weeks of pregnancy, there is a 62-per-cent chance of surviving and babies born after 34 weeks of pregnancy (six weeks early) have survival rates similar to those of babies born at term.
Unfortunately, the earlier the baby is born, the more risk of significant and long-term health problems. These include problems with vision, hearing, learning, behaviour, breathing and feeding.
Risk Factors for PTL
There are factors that increase the risk of PTL but women with no risk factors still have a 2.5- to 5- per-cent chance of delivering preterm. Risk factors can be divided into those that can be modified and those that cannot be changed.
For instance, a woman cannot change her age, but if she has her first baby after adolescence and before the age of 35 there will be lower risk in the pregnancy. She cannot change the fact that she has had a previous preterm birth, abnormality of the uterus, surgery of the cervix or bleeding after the first 12 weeks of pregnancy.
Although nothing is done to change a twin pregnancy into a singleton (one baby) pregnancy, some women with high order multiple pregnancy (five, six or seven babies in one pregnancy) consider reducing the pregnancy to twins or triplets. This will improve the chance of a healthy out-come for mother and some of the children.
The most common risk factor that can be modified is smoking. One-third of women of childbearing age are smokers. Even if a pregnancy is not planned, quitting smoking in early pregnancy reduces the chances of PTL and many other complications of pregnancy. Alcohol and street drugs may cause harm to the fetus and pregnant women are strongly advised to avoid them. Any over-thecounter, natural or herbal products should only be used during pregnancy on the advice of your doctor.
Treatment of certain infections may result in fewer preterm births. Care to avoid trauma by wearing seatbelts and discussing concerns of family violence with your doctor may also be helpful.
Signs and Symptoms of PTL
All pregnant women should be aware of the signs and symptoms of PTL. It is important to realize that many of the symptoms can occur in normal pregnancies too. It may be difficult to tell the difference without an examination.
Many women describe PTL as feeling menstrual-like cramps or regular contractions that may be painful or even painless. The uterus may feel tense or hard when these contractions occur. The cramping may be felt as a change in the low back pain that is common in pregnancy. Some women feel pelvic pressure or fullness in the vagina. The vaginal discharge may change, often times becoming watery, pink or bloody.
Table III Signs and Symptoms of PTL
- Menstrual-like cramping
- Change in low back pain
- Regular contractions (painful or painless)
- Change in vaginal discharge
- Fluid leakage from the vagina
- Bleeding
- Vaginal or pelvic fullness or pressure
- Feeling that something is wrong
If fluid is leaking from the vagina, the membrane sac around the baby may be leaking and this will likely lead to preterm birth. Sometimes, a woman cannot explain it, but she just feels very strongly that something is not right. Women with any of these symptoms should get in touch with their care provider as soon as possible to be assessed for possible PTL.
Diagnosing and Treating PTL
Table II Risk Factors for PTL |
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| Risk factors subject to change | Risk Factors that Cannot Be Changed |
| Smoking | Previous preterm birth |
| Substance abuse | twin pregnancy |
| Infections | Bleeding after first 12 weeks of pregnancy |
| Trauma | Abnormal uterus |
| Maternal age | |
There is no simple test to determine if the symptoms are PTL or not. Since true labour progressively softens, thins and opens the cervix, the cervix is assessed to determine if these changes are occurring. Sometimes ultrasound is used and at other times, pelvic examinations are done to check the cervix for signs of change.
If a woman is thought to be starting PTL, she is likely to be told to stay resting in hospital to see if things settle. Testing may be done to look for causes such as urinary tract infection.
| Birth Weight | % Survival Rate | % Healthy |
| 400 - 499 g | 27% | 4 |
| 500 - 599 g | 27% | 50 |
| 600 - 699 g | 51% | 70 |
| 700 - 799 g | 68% | 63 |
| 800 - 899 g | 80% | 78 |
| 900 - 999 g | 94% | 90 |
| Data from 1991-95 Northern Alberta Neonatal Follow-up Clinic and NICUs Table I |
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Sometimes a medication is used to try to slow the contractions for a while. This will allow enough time to give 24 hours of steroid medication to the mother if she is between 24 and 32 weeks pregnant. These steroids help mature the baby's lungs in case preterm birth does occur. They also reduce, by 40 per cent, the risk of bleeding into the baby's brain that can occur with very early births. Antibiotics are also commonly used to reduce the risk of infection for the mother and baby.
If the pregnancy is at least 34 weeks along, the preterm baby may just require a little extra care and attention in hospital for a while. Earlier than this, special intensive care skills may be needed to deal with all the complications that can occur. For this reason, it might be necessary to transfer a woman in PTL to a hospital that has the equipment and staff to deal with these issues.
Preterm birth continues to be a major cause of health concerns for our newborn infants. By avoiding the risks and recognizing the signs of PTL, it is hoped that our children will get a better head start in life.
FAMILY HEALTH is written with the assistance of |
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FAMILY HEALTH is written with the assistance of |
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