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Reproductive and Birth Outcomes

Premature Births and the Environment

More than a half million babies in the United States—1 of 8—are born prematurely each year. A baby is considered premature if he or she is born before the 37th completed week of pregnancy. Being born premature, or early, is a serious health risk for a baby. It is the leading cause of death among newborn babies. Being born too early can cause lifelong problems such as:

A nurse taking care of a premature baby in the hospital

Although most babies born a few weeks early do well and have no health problems, some have more health problems than full-term babies. For example, a baby born at 35 weeks is more likely to have:

  • Jaundice
  • Breathing problems
  • A longer stay in the hospital

Read more about premature births.

Air pollution, lead exposure, and using some solvents during pregnancy have been related to increases in risk of prematurity or preterm delivery.

Exposure and Risk

Even if a woman does everything "right" during pregnancy, her baby may still be born too early. There are some risk factors associated with preterm birth:

A burning cigarette sitting in an ashtray with a pacifier sitting on table next to it.
  • Carrying multiple fetuses (two, three, four or more)
  • Having a previous preterm birth
  • Problems with the uterus or cervix
  • Chronic health problems such as high blood pressure, diabetes, and clotting disorders
  • Certain infections during pregnancy
  • Cigarette smoking, alcohol use, or illegal drug use during pregnancy
  • Exposure to secondhand smoke

Other possible risk factors are:

  • A mother's age, race, and poverty level,
    • African-American women, women younger than 17 years and older than 35 years, and poor women are at greater risk of having early birth.
  • Male babies, associated with singleton (a single birth) preterm birth,
  • Certain lifestyles and environmental factors, including:
    • Late or no prenatal care,
    • Social and economic factors,
      • Domestic violence,
      • Lack of social support,
      • Stress, and
      • Marital status.
    • Long working hours with long periods of standing,
    • Being underweight or overweight before pregnancy,
    • Spacing of births, less than 6—9 months between birth and the beginning of the next pregnancy, and
    • Environmental chemicals:
      • Exposure to air pollution or drinking water contaminated with lead.


A pregnant woman laying hospital bed while doctor monitors her baby

Preterm births can happen for no obvious reason. Many women who have a premature delivery have no known risk factors. Women who are pregnant or may become pregnant should follow their doctor's advice on how they can have better health and lower their risk of having a premature baby:

  • Quit smoking and avoid secondhand smoke
  • Do not use alcohol or illegal drugs
  • See a health care provider for a medical checkup before becoming pregnant
  • Work with a health care provider to control diseases such as high blood pressure or diabetes
  • Get preconception health care and early prenatal care and continue care throughout the pregnancy
  • Discuss concerns during pregnancy with a health care provider, and seek medical attention for any warning signs or symptoms of preterm labor. Warning signs may include:
    • Contractions every 10 minutes or more often
    • Change in vaginal discharge
    • Pelvic pressure
    • Cramps
    • Abdominal cramps with or without diarrhea.

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