Toronto, Jan 7 (Inditop) Pregnant women have now even more reasons to quit smoking.

Whereas previous research has linked smoking during pregnancy to low birth weight, a new joint Dutch-Canadian study has found that women who smoke during pregnancy risk delivering aggressive kids.

In their study, psychiatry professor Jean Seguin of Montreal University and researcher Stephan Huijbregts of Leiden University in the Netherlands have established that smoking during pregnancy predisposes children to develop violent behaviour.

The problems for children were more compounded if their smoking mother has a history of anti-social behaviour, including problems with the law, use of drugs and dropping out of school.

Other prenatal factors that induce violent behavior in children include the age of the smoker mother. If the mother is younger than 21 and coercive by nature, she will have more violence-prone children, according to the study.

It has also found that the risk of delivering aggressive kids rises among smoking mothers whose annual family income is less than $40,000.

In families with less than $40,000 annual income, heavy smokers had 40 percent chance of having highly aggressive children, compared with 25 percent for moderate or non-smokers, according to the study.

But in the case of families with income higher than $40,000 annually, the gap between heavy smokers and others having violent kids fell to 8 percent, says the study.

“Mothers-to-be whose lives have been marked by anti-social behaviour have a 67 percent chance to have a physically aggressive child if they smoke 10 cigarettes a day while pregnant, compared with 16 percent for those who are non-smokers or who smoke fewer than 10 cigarettes a day,” a Montreal University release has quoted Seguin as saying.

“Smoking also seems to be an aggravating factor, although less pronounced, in mothers whose anti-social behaviour is negligible or zero.”

As part their study, the researchers examined the behaviour of 1,745 children between the age of 18 months and three and a half years.

The researchers found that the effect of smoking (during pregnancy) on aggression in children remains too deep to persist even when other factors – divorce, depression, maternal education and the mother’s age during pregnancy – are not taken into consideration.

The study recommends that low-income women, who are heavy smokers and have a history of anti-social behaviour, become a screening standard for prenatal testing to determine the need for extra support to prevent development of aggressive behaviour in new-borns.

The study, which also involved researchers from Montreal-based McGill University and Quebec City-based Laval University, has been published in the journal Development and Psychopathology.