Magazine article Science News

Mother's Smoking Linked to Child's IQ Drop

Magazine article Science News

Mother's Smoking Linked to Child's IQ Drop

Article excerpt

Preschool children whose mothers smoked heavily during pregnancy scored significantly lower on standardized IQ tests than kids whose mothers did not smoke, according to a new study.

This isn't the first time that researchers have suggested that a pregnant woman's smoking habits might have an impact on her offspring. Last year, a Canadian researcher reported that children born to women who smoked during pregnancy may have subtle auditory difficulties (SN: 7/10/93, p.23).

David L. Olds of the University of Colorado Health Science Center in Denver and his colleagues wanted to find out whether a maternal tobacco habit had an adverse effect on a child's intellectual ability later in life. From 1978 through 1980, the team enrolled 400 women pregnant with their first child.

The researchers asked each woman about her diet, smoking habits, and alcohol or drug use. To verify self-reported smoking behavior, the team measured a nicotine metabolite in urine samples collected from a subset of smokers enrolled in the study.

After delivery, the team continued to check on mothers and their offspring. When the children in the study reached preschool age, Olds and his co-workers began measuring intellectual ability with the Stanford-Binet IQ test.

They report in the February PEDIATRICS that IQ scores of 3- and 4-year-old children whose mothers smoked 10 or more cigarettes daily during pregnancy averaged 9 points lower than those of kids whose mothers did not smoke. When the team controlled for factors known to influence a child's test scores, such as maternal IQ and alcohol use, they found that they could explain some, but not all, of the difference. The children of mothers who had smoked still scored about 4 points lower than the offspring of nonsmoking mothers.

Four points doesn't seem like much, but it is equivalent to the deficit seen in children exposed to moderate amounts of lead, says coauthor Charles R. …

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