smoking while pregnant

A study published in the journal Biological Psychiatry, has shown that women who smoke cannabis during pregnancy risk causing abnormalities to their unborn child’s brain structure, affecting regions related to complex cognition, working memory, and decision making. The findings support the recommendation that pregnant women should not smoke cannabis while they are expecting.


Approximately 2 to 13 per cent of women throughout the world use cannabis during pregnancy. Earlier research had shown that prenatal cannabis exposure has short and long term behavioural effects, but its consequences on brain morphology were not known.

In a recent study, researchers used structural magnetic resonance imaging (MRI) scans to examine the brain development of 54 children, all aged between 6 and 8 years old, as part of an ongoing population-based prospective study in the Netherlands, who were exposed to cannabis while in the womb. In the interim, the researchers found that the majority of the children exposed to cannabis were also exposed to tobacco. For that reason, they also studied the brain scans of 96 children exposed only to tobacco in the womb, as well as 113 control children who were not exposed to either drug. The researchers compared the brain scans of all three groups of children — those who were  exposed to cannabis, those exposed to tobacco, and those unexposed.

The findings, published in Biological Psychiatry, showed that children who were exposed to cannabis in the womb had a thicker prefrontal cortex, when compared to children who were not exposed to cannabis. The prefrontal cortex is a region of the brain that controls decision-making, complex cognition, and is linked to personality. Moreover, compared with children who were unexposed, those exposed to tobacco but not cannabis had smaller brain volume.

The findings suggest that prenatal exposure to cannabis could have important effects on brain development later in life and has different effects than tobacco. This study is significant due to the fact that cannabis use during pregnancy is fairly widespread; the growing decriminalization, medical prescription, and legalization of cannabis increases the possible risk of prenatal exposure.

However, the researchers assert that it is very difficult to conclude that the noted effects in children who were exposed to cannabis were caused by cannabis exposure only since a large degree of tobacco and cannabis use occur together. Care needs to be taken, therefore, when interpreting the results of the study and further research is necessary to investigate the casual nature of the association between prenatal cannabis exposure and abnormalities in brain structure.  Still, the current, in addition with existing, literature does support the significance of preventing smoking cannabis and tobacco during pregnancy.




Written By: Nigar Celep, BASc

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