Smoking During Pregnancy Increases Risk for Birth Defect
July 2, 2008

by Nancy Volkers
InteliHealth News Service

INTELIHEALTH - Mothers who smoke early in pregnancy are more likely to have babies with cleft lip or cleft lip and palate, a study shows.

Other research has shown that smoking increases the risk of these birth defects, which affect about 4,200 babies each year in the United States.

Researchers from the University of Bergen, Norway, studied 573 babies born with a cleft lip or cleft lip and palate. They compared them with 763 babies without these birth defects. Each mother completed a questionnaire when her baby was 4 months old.

Researchers also collected DNA from mothers and babies. They looked for six genes that affect how well the body deals with toxins from cigarette smoke.

Some mothers smoked at least 10 cigarettes a day during their first 13 weeks of pregnancy. The babies of these mothers had nearly twice the risk of cleft lip or cleft lip and palate.

Mothers exposed to secondhand smoke also had an increased risk of having a baby with one of these defects. But this risk was not as high as in the women who smoked.

A gene called NAT2 also appeared to increase the risks of cleft lip or cleft lip and palate. The other five genes did not affect risk.

Smoking and secondhand smoke exposure were not linked with the risk for cleft palate alone. This birth defect occurs in about 2,600 U.S. babies each year.

Cleft lip and cleft palate happen during the fifth to seventh weeks of pregnancy. There are many possible causes. They include infections, alcohol use, not getting enough folic acid and taking certain drugs, such as anti-seizure drugs.

Surgery usually corrects the problem. Children with a cleft palate sometimes have missing or abnormally shaped teeth.

The study appears in the July issue of the journal Epidemiology.