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Smoking in pregnancy increases risk of behavioural problems

Behavioural problems signicant by the time children reach three

OnMedica Staff

Tuesday, 03 November 2009

Smoking during pregnancy significantly increases the risk of having a child with behavioural problems, according to new research.

The findings published ahead of print in the Journal of Epidemiology and Community Health, are based on more than 14,000 mother and child pairs, all of whom were taking part in the Millennium Cohort Study, a large population based study of UK children born between 2000 and 2001 from families receiving child benefit.

The mums were categorised into light and heavy smokers, depending on how many cigarettes they smoked every day during pregnancy.

They were asked to score their three year old children’s behaviour using a validated questionnaire for three to 16 year olds (Strengths and Difficulties Questionnaire), focusing particularly on behavioural problems and hyperactivity-attention deficit disorders.

Behavioural (conduct) problems were based on answers to questions about a child’s temper, the frequency of physical fights with, and bullying of, other children, and being argumentative with adults.

Hyperactivity and inattention were based on answers to questions about the degree of restlessness and fidgeting/squirming a child displayed, and the extent to which the child was easily distracted or their attention wandered.

Almost one in 10 of the mothers said they smoked heavily throughout their pregnancy; a further 12.5% said they smoked lightly during this period, and 12.4% said they stopped smoking while pregnant.

The results revealed that boys whose mothers smoked throughout pregnancy were significantly more likely to have behavioural problems, be hyperactive, and have low attention spans than boys whose mothers did not.

Boys whose mothers smoked heavily throughout pregnancy were almost twice as likely to display behavioural problems. And the sons of light smokers (fewer than 10 cigarettes a day during pregnancy) were almost 80% more likely to have hyperactivity-attention deficit disorders.

The daughters of both light and heavy smokers were significantly more likely to display behavioural problems by the time they were three years old than girls whose mums did not smoke.

But girls whose mothers gave up during pregnancy were significantly less likely to have a combination of behavioural problems and hyperactivity-attention deficit disorders than girls whose mothers had never smoked, although these findings were based on small numbers, say the authors.

This may be because the ability to give up smoking may indicate restraint and an easy going temperament - traits that are then handed down to offspring, suggest the authors.

Smoking during pregnancy may damage the developing structure and function of the fetal brain, which has already been shown to be the case in animals, say the authors. The fetal development of boys may also be more sensitive to this kind of chemical assault, which might explain why boys are more likely to have behavioural problems than girls, they add.



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