Pregnancy is a time of joy, hope, and dedication to the well-being of a new life. Expectant parents are naturally motivated to make choices that give their baby the best possible start—whether that means adjusting diet, changing daily routines, or avoiding harmful substances.

However, despite growing medical evidence about its risks, cannabis use during pregnancy remains a concern. Recent data from the Better Outcomes Registry and Network (BORN), published in JAMA Open, shows that cannabis use in pregnancy in Ontario increased from 1.2% in 2012 to 4.2% in 2022. Other studies suggest underreporting, with actual usage possibly closer to 36% in some groups.

Why Some Expectant Mothers Use Cannabis

• Symptom relief: Some use cannabis to ease nausea or anxiety during pregnancy.
• Recreational use: Others continue previous habits or use to relax.
• Perceived safety: The normalization of cannabis in Canada has led to a belief that it is harmless—even beneficial.

Disturbingly, some cannabis dispensaries in other jurisdictions have reportedly advised pregnant women to use cannabis for morning sickness—a practice that contradicts current medical guidance.

The Science: How Cannabis Affects the Developing Fetus

Cannabis contains THC, a psychoactive compound that alters brain chemistry by interacting with the Endocannabinoid System (ECS). In adults, regular use can reduce ECS function by inactivating CB1 receptors. In pregnancy, THC crosses the placenta and reaches the fetus, which already has active CB1 receptors by 14 weeks post-conception.

This means:

• When mom gets high, baby gets high.
• Fetal brain development occurs in a reduced ECS environment if receptors are downregulated.
• The ECS plays a critical role in “pruning” brain connections for efficient communication—interference can alter brain wiring.

Studies link prenatal cannabis exposure to:

Increased aggressiveness and poorer impulse control in childhood
Reduced attention span
Lower visual problem-solving skills

A Lesson from History

The thalidomide tragedy of the 1950s—where a popular medication for nausea caused severe birth defects—was a stark reminder that substances taken during pregnancy can have devastating consequences. Since then, the guiding principle has been to avoid all unnecessary substances during pregnancy, especially psychoactive ones.

What Healthcare Providers Can Do

• Ask early and often about cannabis use during pregnancy or family planning.
• Clarify details: type of cannabis, method of use, THC concentration.
• Assess for cannabis use disorder (CUD) and offer referrals to support programs if needed.
• Address root causes such as stress, anxiety, or social pressures.
• Educate with empathy: explain that giving cannabis to a newborn would be unthinkable—and using it during pregnancy has the same effect on the baby’s developing brain.

A Call to Action

Clear, multilingual health warnings should be required at all cannabis retail outlets across Canada, making the risks unmistakable to all communities.

Bottom line: Cannabis use during pregnancy is not safe. The risks to brain development, behaviour, and lifelong health are preventable. At Orleans Family Health Clinic, we are committed to supporting patients with Complete, Comprehensive, Caring, and Connected Care—helping expectant families make informed, healthy choices for themselves and their babies.

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Disclaimer: The medical information on this site is provided as an information resource only and is not to be used or relied on for any diagnostic or treatment purposes. This information does not substitute for professional diagnosis and treatment. Please do not initiate, modify, or discontinue any treatment, medication, or supplement solely based on this information. Always seek the advice of your healthcare provider first. Full Disclaimer.