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In most pregnancies, labor starts at about 40 weeks. Labor that starts before the end of the 37th week is considered preterm labor.

Preterm labor can lead to preterm birth. About 1 in every 10 babies born in the United States is born preterm. Preterm birth accounts for 3 of every 4 newborn deaths that are not related to birth defects.

What is going on in the body?

Labor starts with regular contractions of the uterus. The cervix thins out and dilates, or opens up, so the baby can enter the birth canal.

Sometimes labor begins earlier than it should. If preterm labor is caught quickly, delivery can 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 for distress, disorders and disease. If a preterm delivery seems likely, the healthcare provider 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?

• change in the type or amount of vaginal discharge
• pelvic or lower abdominal pressure
• constant low, dull backache
• mild abdominal cramps, with or without diarrhea
• 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 labors, the cause is not known. The factors known to cause preterm labor can be divided into major and minor ones.

• history of preterm labor 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 fetus
• rupture of the amniotic sac leading to premature leakage of the amniotic fluid
• alcohol or drug abuse

• one previous second-trimester abortion
• three previous first-trimester elective abortions
• bleeding after 12 weeks
• weight less than 100 pounds
• any illness with fever
• smoking more than 10 cigarettes a day
• high blood pressure
• chronic illness, such as diabetes
• domestic violence or abuse

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 labor.

Intensive education of women in any high-risk group is important. A wide mixture of social, physical, and pregnancy factors can contribute to preterm labor.

Preterm labor can happen to anyone, but it is more likely in women who do not get prenatal care. So prenatal care is considered an important means of preventing preterm labor and birth.

How is the condition diagnosed?

A woman who notices any of the signs of premature labor should see the healthcare provider immediately. The cervix should be checked to see whether it has begun to change. This is the only way to know for sure if preterm labor has begun.

Home monitoring is also available to help identify preterm labor. The woman wears a uterine contraction monitor several times a day. A recording of the contractions is sent by phone to a central unit so it can be evaluated by doctors or nurses.

Monitoring is used to record the baby's heartbeat and the contractions of the uterus. Pregnancy ultrasound may also be used to estimate the size and age of the baby and to see where he or she is in the uterus.

What are the long-term effects of the condition?

Preterm babies, also called premature babies or preemies, tend to grow more slowly than normal. They may have learning and behavioral problems, and problems with their eyes and ears and with breathing.

What are the risks to others?

Preterm labor 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 preterm labor is suspected, the mother should lie on her left side and drink a quart of water. About half of women respond to bed rest and extra fluids.

The fluids can be given by mouth or through a tube inserted in a vein. This treatment can often quiet the irritable uterus. If there is no sign that the mother or baby is in danger from infection, bleeding, or other problems, the doctor may try to stop preterm labor.

The goal is to allow the unborn child the time he or she needs to grow and mature. Among the many ways to do this are medications that can stop or suppress uterine contractions. Labor should not be stopped if there is any distress in the unborn child, poorly controlled diabetes, severe high blood pressure, preeclampsia, eclampsia, uterine infection, or bleeding.

What are the side effects of the treatments?

• fast pulse
• chest pressure or discomfort
• dizziness
• headache
• feeling of warmth
• shaky or nervous feeling

What happens after treatment for the condition?

If labor 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 monitoring of the unborn child are used. Home monitoring is also available for some situations.