Preterm labor

• Preterm labor and birth can happen to any pregnant woman.
• Women can take steps to reduce the risk of preterm labor.
• Learn the signs of preterm labor and what to do about them.

Pregnancy is a special time for a woman and her family. It is a time of many changes: in a pregnant woman's body, in her emotions and in the life of her family. As welcome as they may be, these changes often add new stresses to the lives of busy pregnant women who already face many demands at home and at work.

Too much stress can be uncomfortable for anyone. In the short term, a high level of stress can cause fatigue, sleeplessness, anxiety, poor appetite or overeating, headaches and backaches. When a high level of stress continues for a long period, it may contribute to potentially serious health problems, such as lowered resistance to infectious diseases, high blood pressure and heart disease.

Pregnant women who experience high levels of stress also may be at increased risk of premature delivery (1). Babies born before 37 completed weeks of pregnancy are considered premature. Babies born too small and too soon are at increased risk for health problems during the newborn period, lasting disabilities (such as intellectual disabilities and cerebral palsy), and even death.

Most women cope well with the emotional and physical changes of pregnancy and other stresses in their lives. A pregnant woman who feels she is coping well with stress taking good care of herself, feeling energized rather than drained, and functioning well at home and work probably does not face health risks from stress.

Pregnant women who are concerned about the level of stress in their lives, and their ability to cope with it, should talk with their health care provider. A health care provider can refer a woman to resources in her community and help her take steps to reduce and cope with stress.

What types of stress may contribute to premature delivery?
The routine everyday stresses that we all face, such as work deadlines and traffic delays, probably don't contribute much to premature birth. It's important to keep in mind that stress is not all bad. When managed properly, a little stress can provide us with the drive to meet new challenges.

But certain types of severe or long-lasting stress may pose a risk in pregnancy. Some studies suggest that women who experience negative life events, such as divorce, death in the family, serious illness or loss of a job, may be at increased risk of premature delivery (1). It is important to remember that while these sorts of stress may increase the risk of a premature birth, most women who experience these sorts of stress do not deliver prematurely.

Women who experience a catastrophic event during pregnancy may be at increased risk for premature delivery. One study found that pregnant women who worked within two miles of the World Trade Center on September 11, 2001, had significantly shorter gestations than women who worked farther from the site (1). Another study found that pregnant women who experienced a major earthquake had shorter gestations (1).

The timing of the event may also influence pregnancy outcome. Studies suggest that women who experienced the World Trade Center attack or an earthquake in the first trimester of pregnancy tended to deliver earlier than women who experienced these catastrophic events later in pregnancy (1).

Chronic stress may play a role in premature delivery. For example, studies suggest that women who are homeless or have serious financial problems may be more likely to deliver prematurely (1). Working outside the home has not been linked to premature birth in most studies. However, women who find their jobs especially physically or emotionally stressful may face some risk (1).

Racism is another form of chronic stress that may contribute to premature birth. Black women may experience stress from racism throughout their lifetime. This may help explain why black women are more likely to deliver prematurely than women from other racial/ethnic groups (1).

Some women may experience serious chronic stress over the pregnancy itself, possibly increasing their risk of premature delivery (1). These women may be especially worried about the health of their baby or about how they will cope with labor and delivery. They should discuss their concerns with their health care provider, who may be able to provide reassurance.

Most women who experience severe stress in pregnancy will not deliver prematurely. Some women may be more vulnerable than others to the effects of stress in pregnancy due to physical or other risk factors (2).

How may stress trigger premature labor?
Researchers do not completely understand how stress may help trigger premature labor. However, certain stress-related hormones may play a role. Maternal stress may cause the release of a hormone called corticotropin-releasing hormone (CRH). CRH, which is produced by the brain and the placenta, is closely tied to labor. It prompts the body to release chemicals called prostaglandins, which help trigger uterine contractions.

Severe or prolonged stress also may interfere with the functioning of the immune system. This could cause a pregnant woman to be more susceptible to infections involving the uterus. Uterine infections are an important cause of premature birth, especially those occurring at less than 28 weeks of pregnancy (1).  

Stress also may affect a woman's behavior. Some women react to stress by reaching for cigarettes, alcohol or illicit drugs, all of which have been linked to premature delivery and other pregnancy complications (1, 3). Use of alcohol and certain illicit drugs also increases the risk of birth defects.

How can a pregnant woman reduce stress?
Each pregnant woman needs to identify the personal and work-related sources of stress in her life and develop effective ways to deal with them. If she feels overwhelmed by stress, she should consult her health care provider.

Pregnancy-related discomforts (such as nausea, fatigue, frequent urination, swelling and backache) can be stressful, especially if a pregnant woman tries to do everything she did before pregnancy. She can help reduce her stress by recognizing that these symptoms are temporary and by asking her health care provider how to cope with them. A woman can also consider cutting back on unnecessary activities when she is uncomfortable.

Many pregnant women experience mood swings during pregnancy. These are caused by hormonal changes and are normal. However, a pregnant woman should keep in mind that mood swings may make it more difficult for her to cope with stress.

A pregnant woman can cope better with the stresses in her life if she is healthy and fit. She should eat a healthy foods, get plenty of sleep, and avoid alcohol, cigarettes and drugs. She also should exercise regularly (with her health care provider's go-ahead). Exercise helps keep pregnant women fit, helps prevent some common discomforts of pregnancy (such as backache, fatigue and constipation) and relieves stress.

Having a good support network (which can include the pregnant woman's partner, extended family, friends and others) also helps a pregnant woman relieve stress.

A number of stress-reduction techniques can be helpful for pregnant women. These include yoga classes for pregnant women, biofeedback, meditation and guided mental imagery. A health care provider may be able to refer a pregnant woman to classes or experts in her community. Childbirth education classes teach relaxation techniques and help reduce anxiety by educating parents-to-be about what to expect during labor and delivery.

Does the March of Dimes support research on stress in pregnancy?
Several March of Dimes grantees are studying the connection between stress reactions and premature birth. These researchers are seeking to determine how stress-related factors in a pregnant woman's environment (including home and neighborhood conditions, racism, occupation, income and major life events) may contribute to her risk of preterm labor. They also are examining how the body physically responds to stress, including increases in blood pressure, heart rate and levels of various stress-related hormones (including CRH) to better understand how stress may trigger preterm labor. A better understanding of the causes of preterm labor may lead to new ways to prevent and treat it.

References

1. Institute of Medicine Committee on Understanding Premature Birth and Assuring Healthy Outcomes, Board on Health Sciences Policy, Behrman, R.E., and Butler, A.S. (eds.). (2006). Preterm Birth: Causes, Consequences, and Prevention. Washington, DC, The National Academies Press.
2. American College of Obstetricians and Gynecologists (ACOG). (2006). Psychosocial Risk Factors: Perinatal Screening and Intervention. ACOG Committee Opinion, number 343.
3. U.S. Department of Health and Human Services. (2004). The Health Consequences of Smoking: A Report of the Surgeon General. Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health.

November 2006