UK researchers examined data on the smoking habits of 14,000 mothers and the behaviour of their children.
Their analysis for the Journal of Epidemiology and Community Health controlled for factors likely to influence the results, including the mother's level of education and socioeconomic status, family stability and problematic parenting.
Boys whose mothers smoked heavily during pregnancy were almost twice as likely to display behavioural problems. Daughters of smokers were significantly more likely to display behavioural problems by the time they were three years old than girls whose mothers did not smoke.
The researchers said: ‘Persistent and in particular heavy smoking throughout pregnancy may be a useful marker of families who need holistic support beyond pregnancy for a range maternal psychosocial problems, parenting and everyday difficulties which continue to characterise these family environments three years after birth. Such support, in addition to targeted smoking cessation interventions, may minimise associated child behaviour problems.'