In the first study of its kind,British researchers have studied children conceived through in vitro fertilisation (IVF) to examine whether children whose mothers smoked during pregnancy were more likely to develop behavioural problems because of the toxic effects of smokingas has been suspectedor because their mothers passed on a genetic predisposition to antisocial behaviour.
The study,which appears to debunk the notion that smoking’s effects on the brain of a developing foetus result in antisocial tendencies,could be the first in a series of attempts to use the approach to disentangle whether genes or various prenatal exposures are responsible for later behavioural problems. The approach could be applied to a host of questionsfor example,whether women who are stressed while pregnant are more likely to have children who are anxious or depressed,as studies suggest.
Anita Thapar,a professor of child and adolescent psychiatry at Cardiff University in Wales,and her colleagues came up with the idea of studying babies born to women undergoing IVF. Thapar and her colleagues studied 779 children,ages 4 to 10,including about 533 who were genetically related to their mothers and 195 who were not. The researchers examined whether those whose mothers smoked were more likely to have been born underweight and whether they developed behavioural problems,such as temper tantrums or frequent fighting.
If its the cigarette smoke having a toxic effect on the brain,youd see the relationship with the childs behaviour regardless of whether the child is related or unrelated to the mothers who smoke, Thapar said. But its not random whether mothers smoke or not. There are a lot of contributing factors,including mothers personalities. What if its those factors that are contributing to the behaviours and not the actual smoking?
As expected,the babies whose mothers smoked were much more likely to be born underweight,regardless of whether they were genetically related to the mothers,the researchers reported in the Proceedings of the National Academy of Sciences. That shows a clear biological effect of smoking on birth weight,regardless of genetics. But antisocial behaviour was more common only in children who were genetically related to mothers who smoked,indicating that a genetic influence was at work.
This suggests there may be inherited factors contributing,and it is not the cigarette smoking having the effect, Thapar said. Other factors,such as a mothers personality traits and other inherited characteristics,are at play during the development of the baby. This says if you find a particular risk factor that looks like prenatal nurture,be carefulit may really be nature.
Thapar and others stressed,however,that complex behaviours are probably the result of a combination of genes and experience. Thapar said the findings in no way suggest it is safe for pregnant women to smoke. Smoking clearly increases the risk of being born underweight,which can increase the risk of a host of medical problems.