A review of a half-dozen studies has shown that as much as 70 percent of pregnant women believe that cannabis use during pregnancy poses little to no risk to their fetuses.

The review, published in the February 2019 issue of Preventive Medicine, was conducted by researchers from UBC's department of family practice.

In a UBC release, lead author Hamideh Bayrampour noted the importance of understanding widespread perceptions about cannabis use in a climate of recent legalization of cannabis.

“As many jurisdictions around the world, including Canada, legalize cannabis, it’s becoming increasingly important for public health officials to understand perceptions of cannabis use and to increase awareness of the health concerns around its use, especially for pregnant women," Bayrampour said in the release.

The UBC researchers reviewed six U.S. studies about women's views on using cannabis while pregnant. Different studies revealed widely different self-reported rates of pot use by pregnant women—from four percent to seven percent, within the past month and year, respectively—while another saw usage jump to 28 percent when hair and urine samples were analyzed.

A majority of pregnant users said they used cannabis to treat nausea early in their pregnancies, and researchers found the highest use rates occurred during the first trimester, with the lowest rates corresponding with the last trimester.

Asked about their perceptions of harm caused by cannabis in general terms, 70 percent of pregnant and nonpregnant responders said they thought pot caused little or no harm. Thirty percent of pregnant women answered "no" when asked if they thought cannabis would harm their baby during pregnancy.

According to the release, there is little research available on health risks of cannabis, so the Society of Obstetricians and Gynaecologists of Canada advises women not to consume the substance while pregnant, while trying to conceive, or during breastfeeding.

The UBC release noted that "some studies have shown an increased risk of problems for pregnant women, including anemia, low birth weight, stillbirth and newborn admission to the neonatal intensive care unit".

“One of our review findings revealed that some people don’t consider cannabis to be a drug,” Bayrampour said in the release. “With this in mind, it’s especially important for health care providers to ask specific questions about cannabis use during pregnancy and breastfeeding to help spark a productive conversation about the potential health impacts and to help support women in their decision to reduce use and quit.”