A new report by researchers at the University of British Columbia has found that up to one-third of pregnant women believe it is safe to ingest cannabis during pregnancy.

The study, published in the journal Preventive Medicine, pored over data from six U.S. studies and found that some women considered cannabis safe because their health-care provider hadn't communicated to them that it wasn't.

Lead author Hamideh Bayrampour, assistant professor in the UBC department of family practice, said the study is important for public health officials to understand perceptions of cannabis use, especially since the drug became legal in Canada.

"What we looked at was perception, not actual risk," Bayrampour said. 

When women were asked about their perception of general harm associated with cannabis use, 70 per cent of both pregnant and non-pregnant cannabis users responded that they perceived slight or no risk of harm.

In one study, when asked if they believed cannabis is harmful to a baby during pregnancy, 30 per cent of pregnant women responded "no." When women were asked to identify substances most likely to harm the baby during pregnancy, 70 per cent chose alcohol, 16 per cent chose tobacco, while only two per cent chose cannabis.

"One of our review findings revealed that some people don't consider cannabis to be a drug," said Bayrampour.

Treat morning sickness

"With this in mind, it's especially important for health-care providers to ask specific questions about cannabis use during pregnancy and breast feeding to help spark a productive conversation about the potential health impacts."

The research found pregnant cannabis users were more likely to be under 25, unemployed, single and African American. Anxiety and depression were also associated with cannabis use while pregnant.

"Based on what we found, their motivation for use was … they wanted to treat their morning sickness," Bayrampour said.

In an effort to get ahead of marijuana legalization in Canada last October, earlier in 2018 the Society of Obstetricians and Gynaecologists of Canada (SOGC) warned pregnant and breastfeeding women that legal pot doesn't mean safe pot.

The society says THC, the main psychoactive component of cannabis, crosses the placenta into fetal tissue and can also accumulate in breast milk — whether from vaping, smoking, or eating.

Potential effects, according to the SOGC include:

• Pre-term labour.
• Low birth weight.
• Lower IQ scores.
• Impulsivity and hyperactivity in childhood.