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Mom's smoking linked to hearing defect.

For pregnant women who smoke, here's another reason to quit: A new study suggests that exposure to cigarette-smoke chemicals in the womb may lead to subtle hearing difficulties for a child later in life.

As part of a long-term study, Peter A. Fried at Carleton University in Ottawa and his colleagues have been monitoring children born to women who smoked cigarettes during pregnancy. The team's earlier studies showed that infants born to smokers responded abnormally to a test of auditory functioning. Normal newborns will extend their arms and legs in the so-called startle reflex when they hear a bell ring, whereas babies born to women who smoked during pregnancy responded less vigorously to the sound of the bell. That finding suggested a problem with the babies' hearing but didn't pinpoint the nature of the difficulty.

When those same children reached the ages of 6 to 11, the team administered a three-part screening battery for auditory processing disorders.

Their analysis revealed a dose-response correlation between prenatal exposure to cigarette smoke and a child's performance on the auditory tests, Fried told scientists attending the Neurobehavioral Teratology Society's annual meeting in Tucson last week. In a dose-response relationship, the higher the exposure to smoke, the poorer the performance on the tests.

That association held even when the researchers accounted for children's exposure to passive smoking.

The Canadian data suggest that abnormalities in auditory processing stem from prenatal exposure to chemicals such as nicotine in cigarette smoke. Such exposure during fetal development, Fried speculates, may adversely affect the outer hair cells in the cochlea, the inner ear that transforms sound waves into nerve impulses.

Children exposed in the womb to chemicals from cigarettes performed below average on all three components of the auditory battery. Compared with children whose mothers had not smoked during pregnancy, their performance showed the greatest impairment on the most complicated exam, which is called the competing word test, Fried says. In it, a word is spoken into each ear simultaneously. The child has to repeat one word and remember the second word, Fried says.

Such results suggest that children born to mothers who smoke may have trouble processing sound. Fried wonders whether such a subtle deficit may create problems for kids when they reach school age. To keep up with their schoolwork, children must quickly. understand the teacher's oral instructions, which often compete with a chorus of other sounds.

Will they outgrow this auditory deficit? Nobody knows. However, Fried points out, even if the ability to deal with spoken information improves, it may be too late. Kids who have fallen behind in their performance at school may have trouble catching up, he says.
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Title Annotation:children of mothers who smoked during pregnancy performed poorer than children of nonsmoking mothers on tests of auditory processing
Author:Fackelmann, Kathy A.
Publication:Science News
Article Type:Brief Article
Date:Jul 10, 1993
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