Because alcohol and tobacco have long been legal substances, there is a lot of evidence about their use during the preconception, pregnancy and perinatal periods. With the legalization of cannabis in Canada, new research on cannabis use may begin to fill the existing evidence gaps and better define its risks.
Because of its illegal status, women may have been reluctant to report using cannabis during pregnancy unless it was being used medically, and research ethics may have prohibited its study. Consequently, much of what we know about cannabis use in pregnancy has come from data gathered during studies on alcohol and tobacco. That is why it now makes sense to link the work of all three substances.
For instance, research shows that women who use cannabis during pregnancy are more likely to smoke cigarettes and use alcohol.1 As well, co-use of tobacco and cannabis is associated small head circumference and may increase other birth defects (cardio, musculoskeletal, and gastrointestinal) compared to no-use and single-use groups.2 This finding of association should be interpreted with some caution based on the number of limitations of the study. Still, it does underscore the need for more robust research in order to understand the association.
Researching all three substances allows for understanding the “clustering of risks” and the interactions between those risks in a way that targeting individual substances cannot do.3 By looking at the clustering of risk as described by researchers, holistic prevention efforts can target social determinants of health that affect poly-substance use.
Linking the findings on the three substances allows researchers to parse out the differences among those who use substances in pregnancy, and the clusters of risk for the substances they use. That will help to further prevention efforts in messaging, discussing substance use with women and their partners, and supporting women with holistic and safe approaches.
1. Ko, J.Y., Tong, V.T., Bombard, J.M., Hayes, D.K., Davy, J., & Perham-Hester, K.A. (2018). Marijuana use during and after pregnancy and association of prenatal use on birth outcomes: A population-based study. Drug and alcohol dependence, 187, 72-78.
2. Coleman-Cowger, V.H., Oga, E.A., Peters, E.N., & Mark, K. (2018). Prevalence and associated birth outcomes of co-use of Cannabis and tobacco cigarettes during pregnancy. Neurotoxicology and teratology, 68, 84-90.
3. Passey, Megan E. et al. (2014). Tobacco, alcohol and cannabis use during pregnancy: Clustering of risks. Drug & Alcohol Dependence, Volume 134, 44–50. https://www.sciencedirect.com/science/article/pii/S0376871613003700#bib0185