Up to one-third of pregnant women do not believe cannabis is harmful to their fetus, according to a review by University of British Columbia researchers. In some cases, women perceived a lack of communication from their health care providers about the risks of cannabis as an indication that the drug is safe to use during pregnancy.

The findings are outlined in a new review, published in Preventive Medicine, in which UBC researchers sought to identify the latest evidence on women’s perspectives on the health aspects of cannabis use during pregnancy and postpartum, and whether their perceptions influence decision making about using the drug. The research suggests that, over the past decade, more women seem to be using cannabis during pregnancy, even though evidence of its safety is limited and conflicting. For the review, researchers identified six studies conducted in the United States that looked at women’s perceptions about cannabis use during pregnancy. Across the studies, the rate of cannabis use among pregnant women varied considerably. In a large US population-based study, nearly 4% of women self-reported using cannabis within the past month, while 7% self-reported using cannabis within the past year. In another study that saw researchers also test hair and urine samples, the rate of cannabis use increased to 28%.

Pregnant cannabis users were more likely to be under age 25, unemployed, single or uninsured, African-American, and to have low income and education, or use other substances such as tobacco and alcohol. A diagnosis of anxiety or depression was also associated with cannabis use during pregnancy. Researchers found that cannabis use rates were highest during the first trimester (7.4%) and lowest during the third trimester (1.8%). Most pregnant users reported using cannabis to treat nausea early in their pregnancy. In one study involving 306 pregnant women, 35% reported being cannabis users when they realized they were pregnant. Two-thirds of those women quit after finding out they were pregnant, but among those who continued to use cannabis, half reported using almost daily or twice a week. When women were asked about their perception of general harm associated with cannabis use, 70% of both pregnant and nonpregnant cannabis users responded that they perceived slight or no risk of harm. In another study, when asked if they believed cannabis is harmful to a baby during pregnancy, 30% of pregnant women responded “no.” When women were asked to identify substances most likely to harm the baby during pregnancy, 70% chose alcohol, 16% chose tobacco, and 2% chose cannabis (see Figure [9]).

While research on the health effects of cannabis is limited, 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. Due to the risk of potential problems, many professional organizations, including the Society of Obstetricians and Gynaecologists of Canada, recommend women not use cannabis when trying to conceive, during pregnancy, and while breastfeeding. Still, some women reported that not having specific counseling provided about the risks of cannabis use suggests that the drug is safe. One finding revealed that some people don’t consider cannabis to be a drug, making it especially important for health care providers to ask specific questions about cannabis use during pregnancy and breastfeeding.

Lead author, Hamideh Bayrampour, is an assistant professor in the UBC Department of Family Practice and an affiliate investigator at BC Children’s Hospital Research Institute. The review article, “Women’s perspectives about cannabis use during pregnancy and the postpartum period: An integrative review,” is available online at www.sciencedirect.com/science/article/pii/S0091743518303773?via%3Dihub [10] (login required).