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Developmental Biology - Autism
Cannabis Use in Pregnancy Linked to Autism Risk
Children whose mothers reported using cannabis during pregnancy at greater risk for autism...
In the largest study of its kind, Ottawa researchers found children whose mothers reported using cannabis during pregnancy were at greater risk of autism. Their incidence of autism was 4 per 1000 compared to 2.42 among unexposed children in pregnancy. These findings were published in the prestigious medical journal Nature Medicine.
Recreational cannabis is now legal in Canada, but that doesn't mean it's safe for people who are pregnant or breastfeeding. Health Canada and the Society of Obstetricians and Gynaecologists of Canada, recommend against pregnant or breastfeeding women using cannabis. Health warnings to this effect appear on cannabis packaging.
"Despite warnings, there is evidence that more people are using cannabis during pregnancy. This is concerning, as we know so little about how cannabis affects pregnant women and their babies. Parents-to-be should be informed of the possible risks, and we hope studies like ours can help."
Mark Walker MD, Chief, Department of Obstetrics, Gynecology and Newborn Care, Ottawa Hospital; Professor, University of Ottawa; senior author of the study.
The research team reviewed data from every birth in Ontario between 2007 and 2012, before recreational cannabis was legalized. Of the half a million women in the study, about 3,000 (0.6 percent) reported using cannabis during pregnancy.
Researchers had previously found cannabis use in pregnancy also linked to an increased risk of preterm birth. In that study, it was found women who used cannabis during pregnancy often used other substances including tobacco, alcohol and opioids.
Considering those findings, in the current study researchers specifically looked at 2,200 women who reported using only cannabis during pregnancy, and no other substances.
They found babies born to this group still had an increased risk of autism as compared to those who did not use cannabis.
Researchers do not know how much cannabis the women were using, how often, at what time during their pregnancy, or how it was consumed. They also note that while they tried to control for other factors that could influence neurological development, their study can still only show association - not cause and effect.
As cannabis becomes more socially acceptable, health-care researchers are mindful that some parents-to-be might think it can be used to treat morning sickness.
"In the past, we haven't had good data on the effect of cannabis on pregnancies. This is one of the largest studies on this topic to date. We hope our findings will help women and their health-care providers make informed decisions."
Daniel Corsi PhD, Epidemiologist, Ottawa Hospital and BORN Ontario, which is affiliated with the CHEO Research Institute.
Women who are thinking about or currently using cannabis during pregnancy should talk to their health-care provider to help make an informed choice about what is best for them and their baby.
Abstract
Cannabis use in pregnancy has increased1,2, and many women continue to use it throughout pregnancy3. With the legalization of recreational cannabis in many jurisdictions, there is concern about potentially adverse childhood outcomes related to prenatal exposure4. Using the provincial birth registry containing information on cannabis use during pregnancy, we perform a retrospective analysis of all live births in Ontario, Canada, between 1 April 2007 and 31 March 2012. We link pregnancy and birth data to provincial health administrative databases to ascertain child neurodevelopmental outcomes. We use matching techniques to control for confounding and Cox proportional hazards regression models to examine associations between prenatal cannabis use and child neurodevelopment. We find an association between maternal cannabis use in pregnancy and the incidence of autism spectrum disorder in the offspring. The incidence of autism spectrum disorder diagnosis was 4.00 per 1,000 person-years among children with exposure compared to 2.42 among unexposed children, and the fully adjusted hazard ratio was 1.51 (95% confidence interval: 1.17–1.96) in the matched cohort. The incidence of intellectual disability and learning disorders was higher among offspring of mothers who use cannabis in pregnancy, although less statistically robust. We emphasize a cautious interpretation of these findings given the likelihood of residual confounding.
Authors
Daniel J. Corsi, Jessy Donelle, Ewa Sucha, Steven Hawken, Helen Hsu, Darine El-Chaâr, Lise Bisnaire, Deshayne Fell, Shi Wu Wen and Mark Walker.
Acknowledgements
This study was supported by ICES, which is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care (MOHLTC). The opinions, results and conclusions reported in this paper are those of the authors and are independent from the funding sources. No endorsement by ICES or the Ontario MOHLTC is intended or should be inferred. Parts of this material are based on data and/or information compiled and provided by CIHI. However, the analyses, conclusions, opinions and statements expressed in the material are those of the author(s) and not necessarily those of CIHI. This study is based in part on data provided by BORN, part of the Children’s Hospital of Eastern Ontario. The interpretation and conclusions contained herein do not necessarily represent those of BORN Ontario. Funding was received from the Canadian Institutes of Health Research (D.J.C., D.E.-C., H.H., D.F. and M.W.). The funder was not involved in study design, analysis or interpretation of data. The funder was not involved in the writing of the manuscript or in the decision to publish.
Funders: This study was funded by the Canadian Institutes of Health Research. Research at The Ottawa Hospital is possible thanks to generous donations to The Ottawa Hospital Foundation. BORN Ontario is supported by the Ontario Ministry of Health and Long Term Care.
About The Ottawa Hospital
The Ottawa Hospital is one of Canada's top learning and research hospitals, where excellent care is inspired by research and driven by compassion. As the third-largest employer in Ottawa, our support staff, researchers, nurses, physicians, and volunteers never stop seeking solutions to the most complex health-care challenges. Our multi-campus hospital, affiliated with the University of Ottawa, attracts some of the most influential scientific minds from around the world. Backed by generous support from the community, we are committed to providing the world-class, compassionate care we would want for our loved ones. http://www.ohri.ca
About the University of Ottawa
The University of Ottawa is home to over 50,000 students, faculty and staff, who live, work and study in both French and English. Our campus is a crossroads of cultures and ideas, where bold minds come together to inspire game-changing ideas. We are one of Canada's top 10 research universities--our professors and researchers explore new approaches to today's challenges. One of a handful of Canadian universities ranked among the top 200 in the world, we attract exceptional thinkers and welcome diverse perspectives from across the globe. http://www.uottawa.ca.
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