Possible Unintended Consequences for Pregnant Women of Legalizing Cannabis Use

Cannabis use during pregnancy is associated with poor maternal and child health outcomes. However, its prevalence is increasing in the US and Canada while perceived risk of cannabis use during pregnancy appears to be decreasing. This may be an adverse unintended consequence of cannabis use legalization.

Studies with humans and other species suggest that cannabis use during pregnancy is associated with low birth-weight (1, 2), neurodevelopmental deficits (e.g., impaired memory and reasoning in infants and children) (2), and maternal anemia (1). Determining the extent of cannabis-related health risks to maternal and child health is complicated by a lack of longitudinal studies in representative samples that control for alcohol, tobacco, other substance use and socioenvironmental characteristics. Nevertheless, given the current evidence, the American College of Obstetricians and Gynecologists, the American Academy of Pediatrics and a recent US Surgeon General advisory recommend that physicians screen and counsel women on the health risks associated with cannabis use, and advise women to abstain (3). However, these recommendations in the US are being made within a socioenvironmental context in which policies and beliefs about cannabis use are becoming increasingly permissive and cannabis is increasingly available. This may explain the increasing trends in cannabis use among pregnant women in the US and some other countries (4–7).

Cannabis use during pregnancy in the US more than doubled since 2002, rising from an estimated 2.4% (4) to approximately 5.0% in 2016 (5). Among pregnant women experiencing nausea and vomiting (i.e., morning sickness), cannabis use is even more prevalent, increasing from an estimated 6.5% in 2009 to 11.1% in 2016 (7). In Canada the prevalence of cannabis use during pregnancy appears to have increased slightly from 1.2% in 2012 to 1.8% in 2017 (6).

A possible explanation for the increasing trends in prenatal cannabis use is cannabis use legalization. Thirty-three US states and the District of Columbia (DC) have legalized cannabis for medical use (8). Additionally, Canada (6), Uruguay (9),11 US states and DC (8) have legalized cannabis for recreational use. Laws that allow medical cannabis use appear to have been associated with increases in cannabis use in the general adult population (10), as well as with increases in the rate of cannabis use treatment among pregnant women (11). Furthermore, the increases in biochemically verified cannabis use among pregnant women (12) and cannabis related adverse consequences in the general population (13), suggest that the increases in the prevalence of self-reported cannabis use during pregnancy may reflect a real increase in the number of women who use cannabis during pregnancy rather than an artifact of more honest reporting post-legalization.

Decreased perception of the risks of cannabis use during pregnancy may also be an unintended consequence of cannabis use legalization. Legalizing cannabis use increases access to and availability of cannabis, particularly via dispensaries. It is possible that dispensaries may be offering advice regarding prenatal cannabis use that is contrary to public health and clinical recommendations (14), leading women to believe that cannabis use during pregnancy is safe. In the US, from 2005 to 2015 the probability of reporting no perceived risk of regular cannabis use increased 13.0% (from 3.5% to 16.5%) among pregnant women who were not current cannabis users, and 39.6% (from 25.8% to 65.4%) among pregnant women who used cannabis in the past month (15). Furthermore, pregnant women may increasingly perceive cannabis use as a safe remedy for morning sickness, especially given the misinformation on the internet about its safety and health benefits, and recommendations from cannabis dispensaries (14). In one state-wide study, the majority of dispensaries was found to recommended cannabis for treating morning sickness; medical dispensaries were more likely than retail dispensaries to make this recommendation; and more than a third of all dispensaries and 41.0% of medical dispensaries told callers – who stated they were 8 weeks pregnant and experiencing morning sickness – that cannabis was safe to use during pregnancy (14). Economic gains from cannabis use legalization put the profit motive in cannabis dispensaries at odds with health messages aiming to prevent prenatal cannabis use.

Social consequences, similar to those associated with alcohol use during pregnancy (e.g., civil commitment; mandatory reporting to child welfare agencies) (16), may result from cannabis use during pregnancy. For example, in the US, many states consider substance use during pregnancy to be child abuse (17) and punishable by law. These laws disproportionately affect low-income, minority women due to discrimination (17). Few other countries criminalize substance use during pregnancy (17). However, policies that do criminalize such substance use put the onus of fetal and child health on the mother, without accounting for socioenvironmental factors that promote substance use behaviors (e.g., cannabis use laws, poor medical advice from cannabis dispensaries, widespread availability of cannabis).

Individuals and their social environments are inextricably linked (18). Therefore, as states and countries continue to legalize cannabis use, identifying and preventing potential unintended maternal and child health consequences of such laws will be critical. To promote optimal maternal and child health, women should abstain from cannabis (and other substance) use during preconception, pregnancy, and lactation. Healthcare providers should support women in these endeavors by respectfully providing health education on the risks of prenatal substance use, and referring women to treatment when needed, as opposed to using punitive measures. Additionally, as part of best practices, dispensaries should be required to post warning signs – similar to alcohol policies (16) – on the risks of cannabis use to include cannabis use during pregnancy.