Discussion
We identified 23 studies that describe the perspectives of just over
10,000 pregnant people about the reasons for, risks and benefits of, and
available information about cannabis use during pregnancy. We did not
identify any studies about the perspectives of lactating people about
using cannabis during lactation, nor did we identify any studies about
the perspectives of partners on the use of cannabis during pregnancy or
lactation.
This review demonstrates the powerful nature of the study design on
research findings. When cannabis is included as one illicit drug used by
someone enrolled in a substance abuse treatment program, the
considerations and priorities are very different than when it is
included as an herbal medicine used by someone seeking a
non-pharmaceutical remedy for nausea and vomiting in pregnancy. Many
studies did not describe the reasons why a person may seek to use
cannabis during pregnancy, or the benefits that users experience from
this substance. Most studies focused on smoked cannabis, and do not
investigate perceptions of risks other forms of cannabis products (e.g.
oils, topical applications, low-THC products).
Concern with fetal harm from prenatal cannabis exposure is a common
theme in this literature. Strikingly, cannabis is almost always compared
by study authors to substances where strong evidence of fetal harm
exists (e.g., alcohol, tobacco, methamphetamines, opioids). This
comparison is carried through to public health and clinical materials
which also commonly group cannabis with these substances, belying the
emergent and equivocal nature of evidence of fetal harm. These common
groupings illuminate the assumptions of researchers but make it
difficult to see that pregnant people may not understand cannabis the
same way. For example, in one included study, participants compared
cannabis to caffeine and fast food, two substances which are
sub-optimal, but fulfill important social and emotional functions for
pregnant people 20.
The precautionary principle holds that when evidence is uncertain, the
appropriate course of action is to err on the side of caution73. Given the evidence showing the potential for
deleterious effects of cannabis use during pregnancy and lactation, the
ideal outcome would be to reduce or eliminate cannabis consumption
during these periods. However, as participants in many of the included
papers described, many receive benefits from using cannabis and fear
that ceasing use may result in greater harm.
Clinicians working with pregnant people who are considering cannabis use
may wish to adopt a harm reduction approach. Harm reduction is
particularly relevant in obstetrical settings where the decision-maker
is not the only person affected by choices about substance use. A harm
reduction approach accepts the inevitability of drug use and works with
users to minimize the associated harms 74. Given the
documented perceptions of benefit and the lack of certainty about harm
of cannabis use in pregnancy, we encourage clinicians and researchers to
inquire about why a person wishes to use cannabis, what benefits
they receive from use. Discussions of risk and benefit should go beyond
physiological impact and include the availability of support, personal
care, agency, and emotional health 75. A strong
relationship between clinicians and their pregnant clients will be
beneficial in order to identify appropriate strategies for harm
reduction, which may include reducing or quitting use, substituting
other drugs or treatments, making a lifestyle change and seeking
consistent prenatal care 74, 76.