Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to page options Skip directly to site content

Reproductive and Birth Outcomes

Low Birth weight and the Environment

Birth weight is the weight of the newborn measured immediately after birth. Birth weight of less than 5.5 lbs, or 2500 grams, is considered low birth weight. A low birth weight infant can be born too small, too early, or both. This can happen for many different reasons which may or may not be related. For example, smoking during pregnancy may make a baby too small (growth retardation), even if that baby is carried the full 40 weeks of pregnancy. For this reason, low birth weight information on the Tracking Network includes only infants who are born full-term.

Compared to infants of normal weight, low birth weight infants may be more at risk for many health problems. Some babies may become sick in the first six days of life or develop infections. Other babies may even suffer from longer-term problems such as delayed motor and social development or learning disabilities.

Exposure and Risk

The following is a list of rick factors that may increase a pregnant woman's chances of having a low birth weight baby in her lifetime:

  • Smoking
  • Drinking alcohol
  • Lack of weight gain
  • Younger than 15 years and older than 35 years
  • Social and economic factors, such as
    • Low income
    • Low educational level
    • Stress
    • Domestic violence or other abuse
    • Unmarried
  • Previous preterm birth
  • Exposure to air pollution (both indoor and outdoor) and drinking water contaminated with lead, which are considered environmental risk factors

Intrauterine (inside the womb) growth retardation can be caused if a pregnant woman smokes or does not gain enough weight during pregnancy.

  Top of Page


Early and regular prenatal care helps identify conditions and behaviors that can result in low birth weight infants. To reduce the risk of having a low-birth weight infant, you can:

  • Quit smoking,
  • See a doctor for a medical checkup before pregnancy,
  • Work with a health care provider to control diseases such as high blood pressure or diabetes,
  • Get preconception health care and early prenatal care throughout the pregnancy,
  • Discuss concerns during pregnancy with a doctor, and seek medical attention for any warning signs or symptoms of preterm labor, and
  • Take a daily multivitamin containing 400 micrograms of folic acid before and throughout pregnancy.
 Top of Page