Children born to mothers who smoked more than a pack of cigarettes a day during pregnancy struggle on tests that measure how accurately a child reads aloud and comprehends what they read.
Researchers from the Yale School of Medicine analyzed data from more than 5,000 children in the Avon Longitudinal Study of Parents and Children (ALSPAC), a study of 15,211 children at the University of Bristol in the United Kingdom.
A research team led by Jeffrey Gruen, M.D., a professor of pediatrics and genetics at Yale School of Medicine, compared performance on seven specific tasks. These tasks included reading speed, single-word identification, spelling, accuracy, real and non-word reading, and reading comprehension.
The researchers examined subjects’ performance on the tasks with maternal cigarette smoking, after adjusting for socioeconomic status, mother-child interactions, and 14 other potential factors.
The researchers found that, on average, children exposed to high levels of nicotine in utero — defined as the minimum amount in one pack of cigarettes per day — scored 21 percent lower in these areas than classmates born to non-smoking mothers. The children were tested at age 7 and again at age 9.
Among students who share similar backgrounds and education, a child of a smoking mother will, on average, be ranked seven places lower in a class of 31 in reading accuracy and comprehension ability, the researchers reported.
“It’s not a little difference — it’s a big difference in accuracy and comprehension at a critical time when children are being assessed, and are getting a sense of what it means to be successful,” said Gruen.
The effects of smoking in pregnancy are especially pronounced in children with an underlying phonological — speech — deficit, suggesting an interaction between an environmental exposure– smoking — and a highly heritable trait, i.e., phonological ability.
“The interaction between nicotine exposure and phonology suggests a significant gene-by-environment interaction, making children with an underlying phonological deficit particularly vulnerable,” he said.
The findings are published in the The Journal of Pediatrics.
Source: Yale University