Cannabis (derived from Cannabis sativa, indica, ruderalis) is now the most commonly used federally illicit substance in the United States. With increasing legalization and social acceptance, its use has grown— including among pregnant and lactating individuals. Yet, medical and public health bodies emphasize that there is no defined safe dose for cannabis during pregnancy or breastfeeding. Use in these periods is associated with potential risks to both maternal and child health.
Obstetrician‑gynecologists and related healthcare professionals are urged to counsel pregnant and lactating patients to cease cannabis use, screening and intervening with evidence-based strategies.
Prevalence, Trends & Context
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Reported prevalence of cannabis use among pregnant individuals reportedly ranges from 3.9% to 16.0%.
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Among reproductive-age individuals (ages ~19–22), use has been as high as ~43%.
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Use is more common in the first trimester, often as a self-management attempt for nausea, vomiting, or appetite changes.
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THC potency in available cannabis products has notably increased over past decades, raising concern about exposure magnitude.
Biology & Mechanisms of Fetal Exposure
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THC (Δ⁹‑tetrahydrocannabinol) is fat‑soluble and crosses the placenta, exposing the fetus.
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Cannabinoid receptors are expressed in fetal tissues as early as ~5 weeks of gestation.
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THC and metabolites can transfer into breast milk, although concentrations are influenced by dose, frequency, and route.
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Because of its lipophilicity, carboxy-THC, an inactive metabolite, can remain detectable for extended periods in biological samples (urine, hair).
Adverse Outcomes & Evidence
While causality is difficult to prove definitively, multiple observational studies and reviews yield associations between prenatal cannabis exposure and various adverse outcomes including, spontaneous preterm birth, low birth weight and small-for-gestational-age infants, increased NICU admissions, and elevated perinatal mortality risk. Along with this, studies in older children and adolescents that were exposed prenatally showed a lower performance on cognitive tests and an increased risk of attention deficits, behavioral problems, and substance use disorders occuring later in life. Similar studies focused around neonatal development have also found adverse effects from cannabis use in that stage of development including, altered arousal, behavioral regulation, and excitability in neonates. Let it be noted that confounding factors including maternal tobacco and alcohol usage make isolating cannabis-only effects challenging.
Guidance & Consensus Recommendations
Support and guidance can range in a plethora of ways. Primary recommendations include screening, counseling, intervention, and support when dealing with an individual who struggles with cannabis use during pregnancy. Screening is an essential first step in the diagnosis of an individual taking part in cannabis consumption while in the prepregnancy, pregnancy, and postpartum periods. Obstetric clinicians should focus on providing concerned counseling to individuals who they find to be partaking in cannabis usage under any of the previously stated phases of pregnancy. This can be anywhere from discouraging an individual from taking part in this behavior to educating them on the unknown risks that it presents to their unborn or recently born child. Offering intervention & support through home visits, text support, digital support is something that should be front of mind when dealing with an individual struggling through this circumstance. Lastly, careful support and constant monitoring should be kept from of mind to help further research on this topic grow.
Practical Counseling Points for Clinicians
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Normalize the conversation. Many patients may underreport use due to guilt or fear of legal consequences. Approach with empathy.
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Explore reasons for use. In pregnancy, many cite nausea, vomiting, anxiety, or insomnia. Discuss alternative treatments or supports.
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Clarify nobody knows a “safe amount.” Emphasize that absence of evidence = not evidence of safety.
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If patient is reluctant to stop, discuss harm-reduction steps (reduce use, avoid high potency, avoid smoking/vaping).
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Follow-up & support: Reassess use regularly throughout pregnancy and postpartum.
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Document consent for any testing or discussion and educate on legal implications relevant in the patient’s jurisdiction.
Gaps & Future Research Needs
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Data on long-term neurodevelopmental impacts remain limited, especially beyond early childhood.
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Few randomized or prospective controlled trials exist due to ethical constraints.
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Impacts of cannabis exposure via breast milk require more robust research.
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Differential effects by dose, route (smoking vs edibles vs vaping), and potency need further clarity.
Given current evidence, the safest recommendation remains abstinence from cannabis during pregnancy and lactation. While patients may perceive cannabis as alleviating symptoms (nausea, anxiety, etc.), clinicians should counsel that there is no medical indication for use during these periods.
Successful counseling depends on trust, open dialogue, and support—not punitive measures. Navigating institutional policies, addressing disparities, and offering resources for cessation are key components of quality prenatal and postpartum care in the era of expanding cannabis legalization.
