One-third of pregnant women do not believe cannabis is harmful to their baby

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While it is widely known that the use of alcohol and tobacco are detrimental to a baby’s development, a new literature review conducted by researchers at the University of British Columbia discovered that pregnant women are far less likely to perceive cannabis use to be harmful in spite of recent evidence to the contrary.

The findings are outlined in a new study, “Women's perspectives about cannabis use during pregnancy and the postpartum period: An integrative review”, published in the journal Preventive Medicine (via ClinicalKey on CKN). The  researchers sought to identify the latest evidence on women's perspectives on the health aspects of cannabis use during pregnancy and post-partum and whether their perceptions influence decision-making about using the drug.

For the review, researchers identified six studies, all conducted in the United States, which looked at women's perceptions about cannabis use during pregnancy, and the motivations behind continued use of cannabis during pregnancy. 

Cannabis use among pregnant women was found to be highest in the first trimester (7.4%), using cannabis to treat nausea caused by morning sickness early in their pregnancy. However the review found that other factors, such as the less expensive cost of cannabis compared to cigarettes and inadequate discussion with healthcare providers on perinatal cannabis use, influenced women’s continued cannabis use.

One study anonymously surveyed women in a prenatal clinic, asking “Do you believe marijuana is harmful to a baby during pregnancy?” In this particular survey, 30% of women responded “no.” When the women were asked to identify substances most likely to harm the baby during pregnancy, 70% chose alcohol and 16% chose tobacco, while only 2% chose cannabis.

In both general and pregnant populations, perception of harm is a strong determinant of cannabis use, as users are far more likely to view cannabis as a low- or no-risk drug.

"Our research suggests that, over the past decade, more women seem to be using cannabis during pregnancy than ever before, even though evidence of its safety is limited and conflicting," said lead author Dr. Hamideh Bayrampour. “Sometimes healthcare providers don’t communicate [the risks of prenatal cannabis exposure], just because of the uncertainty.”

The study also found that women who used cannabis during their pregnancy perceived a lack of communication of prenatal health risks as an indication that cannabis use did not pose risks to their pregnancy. "As many jurisdictions around the world, including Canada, legalise 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." Dr. Bayrampour said.

New evidence shows newborn health is harmed by cannabis 

Emerging evidence has linked perinatal cannabis use to low birth weights and increased neonatal intensive care unit admission.

Presented at the Society for Maternal-Fetal Medicine 2019 Annual Pregnancy Meeting this month, a retrospective chart review of 1,062 newborns delivered in Colorado, Virginia and Tennessee showed that cannabis-exposed newborns were 82% more likely than unexposed newborns to be of low birth weight, 79% more likely to be born before term, and 43% more likely to be admitted to the NICU. 

All birth outcomes examined were significantly worse for infants exposed to cannabis than for unexposed infants, after factors that could influence birth outcomes, such as mother's age, marital status, race, parity, socioeconomic status, and in utero exposure to tobacco, alcohol, benzodiazepines, and opioids, were controlled for. The fact that the worse outcomes were independent of other risk factors that are common with cannabis use, such as other drug exposure and sociodemographic risks, is notable.

“Some people don't consider cannabis to be a drug”

Across the studies examined by Dr. Bayrampour, the rate of regular cannabis use among pregnant women varied considerably, ranging from 4% of women who self-reported using cannabis within the past month in one study, to 28% when researchers tested hair and urine samples. In another study involving 306 pregnant women, 35% reported being cannabis users when they realised 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.

Due to the risk of potential problems, many professional organisations, including RANZCOG, recommend that women do not use cannabis when trying to conceive, during pregnancy and while breastfeeding.

Still, some women reported that the absence of specific counselling about the risks of cannabis led them to believe that the drug is safe.

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