Mandatory Signs Describing the Risks of Cannabis Use During Pregnancy: Do They Work?

While we have seen decreasing rates of alcohol and tobacco use during pregnancy over the last few decades, the use of cannabis during pregnancy is on the rise. Some women use cannabis recreationally; however, qualitative studies indicate that pregnant women report using cannabis to manage a range of psychological symptoms, including anxiety and depression.

Multiple studies indicate that the use of cannabis during pregnancy is not without risk. For example, in a large cohort study from Canada including 1,280,447 singletons births, pRenatal cannabis use was associated with an increased likelihood of preterm birth, low birth weight, small-for-gestational age and major congenital anomalies with prenatally exposed female infants showing evidence of greater susceptibility.

Given concerns surrounding the known and unknown risks associated with cannabis exposure during pregnancy, professional organizations, including the American College of Obstetricians and Gynecologists (ACOG)have urged greater vigilance, highlighting the importance of screening for cannabis use and educating patients about the risks of cannabis use in women of childbearing age.

Nonetheless, many women are not aware that the use of cannabis during pregnancy can carry risks.

Mandatory Sign Policies: Do They Work?

In order to better inform consumers, some states where recreational cannabis is legal have enacted mandatory warning signs policies, requiring businesses to post point-of-sale signs describing a range of warnings about the harms of using cannabis during pregnancy.

But do they work? Do they result in decreased use of cannabis by pregnant women? Do mandatory sign policies result in better outcomes for infants? More than a few studies have questioned the effectiveness of mandatory sign policies as a means of reducing substance use in pregnant women. For example, a study from the state of Washington, where mandatory sign policies were in effect, observed worse outcomes–a decrease in birth weight and higher rates of low birth weight babies–after the enactment of mandatory sign policies.

Undoubtedly there are multiple factors influencing a woman’s decision to use or to abstain from cannabis use during pregnancy, and there may be more and less effective methods of informing women about potential risks. What is concerning about the Washington study is that what seems like a pretty straightforward way of disseminating information may actually have unintended consequences.

However, considerable questions remain as to why warning signs for substance use during pregnancy may have unintended adverse consequences. One possibility is that warning signs increase fears of punishment and thus influence pregnant people to avoid prenatal care. Another is that warning signs may lead people to believe their substance use has already irreversibly harmed their baby and thus it is too late to stop use. From the larger health communications literature, people who use cannabis could experience message fatigue21 and tune out or distrust information in messages. Research has not yet examined these mechanisms.

A recent study examines how cannabis warning signs could impact birth outcomes, specifically whether the signs’ impact might differ depending on preexisting cannabis-related beliefs and use. The researchers surveyed a sample of pregnant and recently pregnant individuals and examined how warning signs affected the use of cannabis during pregnancy and how individuals perceived the warning signs.

Are the Warning Signs Helpful or Harmful? It Depends

This cross-sectional study analyzed data from a population-based online survey of pregnant and recently pregnant (within the past 2 years) individuals and was conducted from May to June 2022. Participants were questioned about their use of cannabis during pregnancy and their beliefs regarding the safety of cannabis use during pregnancy, whether cannabis use during pregnancy should be punished, and the stigma associated with cannabis use during pregnancy.

A total of 2,063 pregnant or recently pregnant people reported using cannabis during their pregnancy. Among people who used cannabis during their pregnancy, living in a warning sign the state is associated with the belief that cannabis use during pregnancy is safe and that people who use cannabis during pregnancy should not be punished. However, among people who did not use cannabis before or during pregnancy, living in a state with mandatory warning signs was associated with the belief that the use of cannabis during pregnancy was not safe, that people should be punished for using cannabis during pregnancy and that cannabis use was stigmatized. Warning signs policies were not associated with increased use (adjusted odds ratio, 1.11 [95% CI, 0.22 to 5.67]).

Although the primary goal of the mandatory warning signs policy is to reduce the use of cannabis during pregnancy, this study suggests that the warning signs did not reduce the use of cannabis during pregnancy. Furthermore, the signs did not shift users’ opinions regarding the safety of cannabis use during pregnancy.

Seems like we need to find a more effective strategy to reduce the use of cannabis during pregnancy.

Ruta Nonacs, MD, PhD


Roberts SCM, Zaugg C, Biggs MA. Association of Mandatory Warning Signs for Cannabis Use During Pregnancy With Cannabis Use Beliefs and Behaviors. JAMA Netw Open. 2023 Jun 1;6(6):e2317138.

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