Science / Medicine : Low Birth Weight Tied to Smoking

An estimated two-thirds of all American babies who die in infancy have low birth weights. A 10-year study now confirms a strong link between a mother’s smoking during pregnancy and the chances she will have an underweight baby.

The study, by the federal Centers for Disease Control in Atlanta, involved nearly 248,000 women, 30% of whom smoked during pregnancy. Researchers defined low birth weight as anything under 5 pounds, 8 ounces.

Fifty-one percent of the women in the study were Anglo, 33% black and 12% Latino. The researchers found that the risk of delivering a low-birth-weight baby increased with a woman’s age, and that black women who smoked were more than twice as likely as white women to have underweight children. In addition, women smokers who were underweight ran a notably greater risk of having a low-weight baby than did nonsmokers.

The study concluded that a decrease in the oxygen supplied to the fetus, not decreased caloric consumption during pregnancy, is the likely mechanism that links cigarette smoking to low birth weight. Infants born with an insufficient supply of oxygen to their brains are prone to lapse into comas or suffer convulsions, and face an increased risk of brain hemorrhages.