Preterm labour is labour that begins before the end of 36 weeks of pregnancy.
Preterm labour is of special concern because it often leads to the birth of a baby before the start of the 37th week of pregnancy. Being born too early—before a baby is fully ready for life on its own—is a major cause of illness and death in infants. Although only 8-10% of babies born in the United States are preterm, preterm birth accounts for more than 60% of newborn deaths, not counting those related to birth defects. That’s why preventing preterm birth is so important.
This article will outline the risk factors and signs of preterm labour and ways to detect it at an early stage. It will also give you some basic information on what to expect if you are hospitalized for monitoring or if you give birth to a preterm baby.
What Is Preterm Labour?
Labour takes place when regular contractions of the uterus occur along with certain changes in the cervix (opening of the uterus). These changes in the cervix include thinning out (effacement) and opening up (dilation) so the baby can move from the uterus into the birth canal. It is not certain exactly what causes labour to begin. Hormones produced by both the fetus and the mother and changes in the uterine muscle all play a role.
In most pregnancies, labour begins around 40 weeks. Labour is considered preterm if it begins before the end of the 36th week. Preterm labour can be diagnosed only after it is determined whether the cervix has begun to change.
Causes of Preterm Labour
It is not clearly known why some women go into preterm labour and others do not. It is also uncertain whether preterm labour is a normal process that is somehow triggered early, or whether it is started by some other problem, such as infection. For about two-thirds of women who begin labour before the end of 36 weeks, the exact cause of preterm labour is never known.
What is known is that preterm labour seems to be linked to a number of risk factors. Women who have little or no prenatal care—a program of care for a pregnant woman before the birth of her baby—seem to be at increased risk for preterm labour. Good prenatal care is important in any pregnancy, but it is even more important if you are at risk for preterm labour.
A number of other factors have also been linked to preterm labour. Some of these factors have to do with the mother’s medical history or health, as well as her previous and current pregnancies. Having one or more of these factors does not mean that you will have pre-term labor—only that you are at increased risk of giving birth to a preterm baby during this pregnancy (see box).
In addition, exposure to the drug DES, or diethylstilbestrol, while you were a fetus may increase your risk of preterm labour. DES is a drug that was given to many pregnant women during the 1950s and 1960s. If your mother took DES when she was pregnant with you, this may increase your own risk of preterm labour. It has been found to cause abnormalities such as a T-shaped uterine cavity or abnormal cervical tissue in some daughters of women who took it during pregnancy.
Risk Factors for Preterm Labour
Preterm labour in the current pregnancy
Previous preterm labour or history of preterm birth
Current multiple pregnancy—two or more fetuses
Several induced abortions—the planned ending of a pregnancy
Abnormalities of the cervix, such as incompetent cervix, or of the uterus, such as malformations or fibroids
Abdominal surgery in current pregnancy
Serious infection in the mother
Bleeding in the second trimester of current pregnancy
Underweight in the mother—weight less than 45kg
Problems with the placenta, the thick pad of tissue in the uterus that provides nourishment to the fetus, may also lead to preterm labour. One such problem is placenta previa, a condition in which the placenta lies very low in the uterus so that the cervix is partly or completely covered.
And, finally, there are factors linked to the fetus that make preterm labour more likely. For instance, too much fluid in the amniotic sac that surrounds the baby is a risk factor. Certain birth defects in the fetus also increase the risk of preterm labour.
Despite what is known about these risk factors, much remains to be learned about preterm labour. Half of the women who go into preterm labour have no risk factors.
Risks to the Fetus
Preterm labour is of serious concern because preterm infants often have problems coping with life outside the uterus. Depending on how early they are born, preterm babies often need special medical care in order to breathe, eat, and keep warm. The medical problems described here are most common and most severe for infants born before 32 weeks of pregnancy, but they may affect all preterm infants to some extent.
Because preterm babies are usually of low birth weight (weighing less than 5-1/2 pounds at birth), their health and survival may be threatened. Babies born too early often have organs that are not developed enough to function properly. For instance, the lungs of a preterm infant are often not fully developed, and the newborn may have trouble getting enough air. This condition is called respiratory distress syndrome (RDS). Apnea, or interrupted breathing, often occurs in preterm and low-birth-weight babies in the first days or weeks of life. A preterm baby may also have problems with swallowing, making it necessary for him or her to be fed through a tube. Also, since preterm babies often don’t have enough body fat, they may have trouble maintaining body temperature.
Signs of Preterm Labour
The first signs of preterm labour are often subtle and painless and may begin slowly. If preterm labour is discovered early enough, preterm delivery can often be prevented or postponed, giving your baby extra time to grow and mature.
Sometimes the signs that preterm labour may be starting are fairly easy to detect. For example, when the membranes rupture (your “water breaks”), you will feel a continuous trickle or gush of fluid from the vagina. Other times, though, the signs of preterm labour are very mild and may be very hard to detect. The box shown here lists the early signs of preterm labour. If you experience any of these signs, don’t wait. Call your doctor right away.
Warning Signs of Preterm Labour
Early diagnosis provides the best chance to treat preterm labour effectively. Call your doctor right away if you notice any of these signs:
Change in type (watery, mucous, or bloody)
Increase in amount
Pelvic or lower abdominal pressure
Low, dull backache
Abdominal cramps, with or without diarrhoea
Regular contractions or uterine tightening
If Warning Signs Occur
If you notice signs that preterm labour may be starting, your doctor may want to see you right away. This can be a tense and frightening time, so it is wise to be prepared for what may happen and what steps your doctor may take to treat preterm labour, if it is diagnosed.
To find out whether you are actually in preterm labour, you will be examined to see whether your cervix has begun to change. Fetal monitoring tests are usually used to record the heartbeat of the fetus and contractions of the mother’s uterus. A procedure called ultrasound, in which sound waves are used to create an image of the fetus may be used to estimate the size and age of the fetus and to determine its position in the uterus. You may be watched for a time and then examined again to see whether your cervix continues to change, which confirms preterm labour.
If labour is detected at its earliest stages, and there are no apparent signs that you and your baby are in danger from infection, bleeding, or other complications, your doctor may try to stop the labour. Sometimes bed rest and hydration—extra fluids are given by mouth or through a tube inserted into a vein—are enough to stop contractions.
Your doctor may treat preterm labour by giving you drugs that can stop or suppress uterine contractions. These drugs are usually given by injection but can also be given by mouth.
If you are not actually in preterm labour or if labour is stopped, you may be able to go home. Otherwise, you may need to stay in the hospital for a while. This will depend on what the doctor’s exam reveals and other factors.
Steps for Women at Risk
If you have had signs of preterm labour, your doctor may advise certain measures to lower the risk to your baby and try to maintain your pregnancy until term. These steps may involve changes in your lifestyle, learning how to monitor your contractions, or taking drugs prescribed by your doctor to stop the contractions.
A)Life Style Changes
If you are at risk for preterm labour, you should take special care of yourself during pregnancy. A healthy pregnancy—including early prenatal care, good nutrition, and adequate rest—is your best defence. Your doctor may ask you to come in more often for exams and tests. You should give up unhealthy habits, such as drinking alcohol and smoking cigarettes and stay away from drugs other than those advised by your doctor.
Women at risk for preterm labour usually do not have to give up their jobs unless preterm labour has actually been diagnosed. Most women are advised to avoid lifting and other strenuous or tiring tasks during pregnancy. If you take childbirth preparation classes, the teacher may advise you to skip certain exercises. Women at risk may also be advised to cut down on travel. Also, nipple preparation for breastfeeding may have to wait until after the end of the 36th week, since stimulating the nipples can sometimes lead to uterine contractions that may start labour. Talk to your doctor about these and other changes you may need to make in your daily routine.
If you have a history of preterm labour or have signs of preterm labor, you may wonder about having sex during pregnancy. Many women worry that the uterine contractions that often follow intercourse and orgasm will continue and lead to preterm labour. Although in most cases the contractions stop, these are natural and realistic concerns that should be discussed with both your partner and your doctor. Your doctor may advise you to restrict sexual activity or to monitor yourself for contractions after intercourse. Your doctor may also ask that your partner use a condom during sex, since this may help decrease the chance of infection.
B)Monitoring for Contractions
If you are at increased risk for preterm labour, your doctor may advise you to monitor yourself after about 20 weeks of pregnancy for signs of uterine activity or tightening. Monitoring may be done by palpation—by hand. If you monitor yourself by palpation, it is best done at the same time each day so that you will be sensitive to any changes in uterine activity if they occur.
Monitoring by palpation consists of lying down and feeling gently over the entire surface of your lower abdomen with your fingertips. You are feeling for a firm tightening over the surface of your uterus. Usually, these feelings of tightening are not painful.
If you detect contractions, turn onto your side and continue monitoring for an hour. Keep track of when each contraction starts and ends and the total number of contractions per hour. Having some uterine activity before 37 weeks of pregnancy is normal. But if your contractions are occurring more than once every 10 minutes (six or more per hour), you need to call your doctor right away. You may be in preterm labour.
Remember, a diagnosis of preterm labour can be made only after a pelvic exam to see whether your cervix has begun to change. A note of caution: just because you have had contractions without cervical change is no guarantee that your cervix won’t change the next time you have contractions. You should contact your doctor or nurse each time you have more than six contractions per hour.
If you have had preterm labour or birth, bed rest may be prescribed. The kind of bed rest advised can vary. It may mean that you will have to stop working. It can be partial bed rest, where you can get up, go to the bathroom, and have limited activity. It may involve staying off your feet and restricting certain activities, such as climbing stairs. Or it may be total bed rest.
For most women, having to stay in bed week after week, even month after month, is very difficult. You may often feel moody, helpless, and depressed. Sometimes you may feel that the frustration and boredom just aren’t worth it, and you may be tempted to resume your activities. It can be especially hard for you to take care of your other children and spend time with your partner and friends.
If you must stay in bed, structuring your life can help lessen these feelings of inadequacy and frustration. Planning your days, including a change into day clothes and regular time with family and friends, can help. Line up tasks that you can do in bed, perhaps with a phone nearby. Arrange for help with housework and shopping, if possible, and don’t be afraid to rely on others for support.
Since you are inactive, you may need to make changes to your diet so you take in fewer caloriesHigh-fibre foods and plenty of fluids will help avoid constipation. You may want to talk to your doctor about exercises you can do in bed to improve circulation.
D)Drugs to Stop or Suppress Labour
Drugs may be prescribed for you to take after you have had signs of preterm labour. As with all medications, these drugs can have side effects. Each woman responds differently to these drugs. Most women find that the following side effects, if present, lessen with time:
Chest pressure or discomfort
Feeling of warmth
Shaky or nervous feeling
If any of these symptoms persists or is unusually strong, your medication may need to be altered, so you should alert your doctor if they occur. Even if labor has been stopped, you will need to keep taking medication until the end of your 36th week of pregnancy to help keep preterm labor from happening again, unless your doctor advises otherwise.
Sometimes preterm labour may be too advanced to be stopped. Or there may be reasons, such as infection, high blood pressure, bleeding, or signs that the fetus may be having problems, that the baby is better off being born, even if it is early.
Preterm labor and delivery involve risks that re-quire care in a hospital with special facilities. In order to receive this care, you or your baby, or both of you, may have to be moved to another hospital. Preterm babies are more likely to be delivered by cesarean birth, in which the baby is born through a cut made in the mother’s abdomen and uterus.
Your Preterm Baby
It’s important to know that your preterm baby may not look like what you expected. Most preterm babies appear quite red and skinny because they have little fat under their skin and their blood vessels are close to the surface. After a few days, your preterm baby may develop jaundice, causing his or her skin to appear yellow. This condition is usually temporary.
Many preterm babies are tiny and fragile. They are not ready to live on their own, so they may be cared for in a neonatal intensive care unit (NICU) for weeks and sometimes months. Your baby may be placed in an incubator to keep warm, may be fed through a tube, may need a respirator to help with breathing, and may be monitored by specially trained nurses and complicated equipment. Today, with this special care, even very early, low-birth-weight babies have a much better chance of survival than in past years.
NICUs are often very busy, crowded places. At first, you may feel that everyone else is taking care of your baby and there is no place for you. You may wish for privacy. You may feel frightened and awkward. It may help to know that these are normal reactions to this new and bewildering situation. Talk to the nurses and doctors caring for your baby. They will help you with any questions you may have about your baby.
It may also help to know that your baby needs you in order to thrive. Your baby needs to hear your voice and to feel your touch. Contact with the baby is important for the parents, too. As soon as possible, talk to your baby. Stroke him or her in the incubator. After a time, you may be able to hold and cuddle your baby for longer periods of time and help with the baby’s care.
Although the exact causes of preterm labour are not known, there are things you can do to improve your baby’s chances of being born healthy. Regular prenatal care is an important first step in the prevention of preterm labor. By leading a healthy life style, being alert to warning signs, and following your doctor’s advice, you can do your part to improve your chances of having a healthy baby.