The study - published in the journal Neuropsychopharmacology - looked at over 200 children and found those whose mums smoked while expecting went on to have infants with smaller grey matter. They compared these findings with a control group of 113 children who had not been exposed to cigarettes in the womb.
Lead researcher Dr Hanan El Marroun from the Erasmus Medical Centre in Rotterdam said they put the findings down to tobacco affecting the baby's development by destroying neurons and reducing oxygen to the foetus because of the narrowing of blood vessels.
Dr El Marroun said: "It's well known cigarette smoking can cause serious health problems including cardiovascular diseases and cancer.
"Smoking during pregnancy has also been shown to adversely affect offspring health. Yet up to 25 per cent of pregnant women report smoking during pregnancy.
"Smoking during pregnancy has been linked to spontaneous abortions, reduced growth and sudden infant death syndrome."
He added that it had also been lined the 'behavioural and cognitive problems' during childhood and adolescence.
"Furthermore, evidence is accumulating prenatal tobacco exposure is related to psychiatric disorders and mortality from childhood to young adulthood," Dr El Marroun said, concluding that 'overall, our findings suggest long-term effects of pre-natal tobacco exposure on brain development and emotional problems in young children'.
He suggested more research is needed to explore the structural and functional neuro-developmental effects of prenatal exposure to tobacco.
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