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Low Birth Weight Babies: Causes and Prevention

written by: Diana Cooper • edited by: Lisa Lambson • updated: 10/8/2010

Low birth weight babies are more at risk for complications. Learn the causes of low birth weight and know what you can do to help prevent it.

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    Low Birth Weight Babies

    Most newborns weigh 2700-4000 grams (6-9 pounds), with the average weight being about 3400 grams (7.5 pounds). Newborns who weigh below 2500 grams (5.5 pounds) are usually classified as low birth weight babies.

    It is estimated that 1 out of 12 babies in the United States are born with low birth weight. The number of deaths have reduced greatly with advances in medical care but a small percent who do survive develop cerebral palsy, mental retardation, learning problems, and hearing and vision loss.

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    Causes of Low Birth Weight

    Women who are more at risk of having low birth weight babies include:

    • African Americans (two times more likely than Caucasians).

    • Teen mothers (especially under the age of 15).

    • Women giving birth to 2 or more babies (more than half of multiple birth newborns have low birth weight compared to 6% of single birth newborns).

    Causes of low birth weight include:

    • Premature birth. Newborns born before 37 weeks gestation have less time to grow and gain weight in the uterus. The latter part of pregnancy is when the fetus gains most of his or her weight.

    • Intrauterine growth retardation (IUGR). This is when the fetus does not grow well during pregnancy because of a complication. Premature and full-term babies can be IUGR. Full-term babies are small but they are normally physically mature. Premature babies are very small and physically immature.

    • Birth defects. Structural abnormalities and genetic conditions can limit normal development. A fetus with a birth defect is more likely to be born prematurely.

    • Chronic health problems in mom. Diabetes, high blood pressure, and heart, lung, and kidney problems can cause low birth weight. Visit your health care provider as recommended.

    • Infections in mom. Some infections, especially uterine infections, increase the risk of pre-term delivery.

    • Infections in the fetus. Viruses, such as chicken pox, rubella, cytomegalovirus (CMV), and toxoplasmosis can causes birth defects and slow fetal growth. Staying away from cat feces and eating properly cooked meats can help prevent toxoplasmosis. Your health care provider should inform you of this and more. If you have questions, ask.

    • Placental problems. The flow of blood and nutrients can be reduced to the fetus and limit growth.

    • Smoking. Smokers are about twice as likely to have low birth weight babies as nonsmokers. If you smoke, ask for help in quitting. Find natural ways to quit smoking.

    • Alcohol and illicit drugs. Both can cause birth defects and limit fetal growth. Some drugs, like cocaine, can cause pre-term delivery. Avoid alcohol and drugs. Ask for help if needed.

    • Poor nutrition and inadequate weight gain during pregnancy are other causes of low birth weight. Normal weight gain during pregnancy is usually 25-35 pounds. Learn about healthy eating during pregnancy.

    Low birth weight babies who are full-term and without complications can usually go home as soon as they are able to maintain their body temperature and eat well enough so they are no longer losing weight. Normally, newborns lose about 10% of their birth weight by 3-4 days of age because of limited food intake and loss of excessive extracellular fluid and meconium. Birth weight is usually regained by the tenth day of life. Premature babies and babies with complications can take longer depending on their condition.