Navigating Cannabis Use During Pregnancy and Breastfeeding—Why Legalization Doesn't Mean Safe (THC and Fetal Brain Development)

The use of cannabis during pregnancy and lactation is viewed by experts as highly concerning, even dangerous, due to the critical role of the endocannabinoid system (ECS) in fetal neural development.

• Presence and Function in the Fetus: Cannabinoid receptors (CB1 and CB2) are present and active in the developing fetus and newborn. Endogenous cannabinoids are found at much higher levels in the fetus than after birth and decrease as development progresses, suggesting that cannabinoid signaling is central to brain wiring.
• The Risk of THC Exposure: THC, CBD, and related compounds are highly lipophilic and easily cross both the blood-brain and placental barriers. When ingested, they outcompete natural cannabinoids, interfering with the normal pattern of signaling that guides brain development. Experts stress that altering this system during gestation is extremely concerning and represents an “experiment that’s ongoing.”
• Statistics and Misinformation: Up to 15% of pregnant mothers self-report cannabis use in some form, with some estimates as high as 20%. Legalization has created a false perception of safety. Studies show that 80–85% of dispensary staff in one Colorado study recommended cannabis for morning sickness, spreading medically incorrect advice.
• Lactation: THC and CBD are lipophilic and transfer into breast milk, raising similar concerns for newborns during nursing.

The audience is deeply anxious about the potential harm to unborn children from cannabis use during pregnancy, especially given its rising prevalence. Concerns include:

• Irresponsible Dispensary Advice: Pregnant women report receiving misleading and dangerous health recommendations from dispensary staff encouraging THC for nausea.
• Lack of Research/Data: Mothers facing severe morning sickness feel trapped between dangerous pharmaceutical options and poorly studied cannabis use, suspecting research gaps are financially motivated.
• “Legal is Safe” Misconception: Legalization has led to widespread misunderstanding that cannabis is harmless, despite THC crossing both the blood-brain barrier and appearing in breast milk.

Total abstinence from cannabis (THC and CBD) is strongly advised during pregnancy and lactation. Because cannabinoid receptors guide fetal brain wiring, substituting natural endocannabinoids with THC may cause irreversible developmental disruption. If experiencing extreme nausea or appetite loss, consult a qualified physician rather than relying on unverified advice.

• Andrew Huberman: Huberman approached this subject with a sense of urgency and gravity, drawing on his expertise as a developmental neurobiologist. He explained that endogenous cannabinoids play a vital role in guiding fetal brain development and that when THC or CBD is consumed, these external compounds outcompete the body’s natural endocannabinoids—a process he described as “absolutely central” to brain wiring. Huberman cited the shocking statistic that 15% of pregnant women in the U.S. report cannabis use and underscored that legalization should never be interpreted as safety. He issued clear warnings that cannabis use during pregnancy and breastfeeding is dangerous and emphasized that medical professionals universally advise against it.
• Dr. Matthew Hill: Dr. Hill noted the high prevalence of cannabis use among pregnant individuals, with some reports reaching 20%, and pointed out that results differ depending on self-reports versus biological testing. He explained that many women use cannabis to manage morning sickness, sometimes believing it to be a safer option than pharmaceutical drugs, particularly in light of historical tragedies such as thalidomide-related birth defects. Hill strongly condemned the reckless and unethical recommendations made by some dispensary staff who advise pregnant women to use cannabis for nausea, calling such behavior dangerously irresponsible given the lack of safety data and potential risks to fetal development.

If pregnant or breastfeeding, stop using all THC and CBD products immediately. Both compounds cross into the fetus and breast milk, posing unknown but potentially serious risks to brain development.

• Mistake: Assuming edibles or CBD are safer alternatives to smoking.
  Fix: Both THC and CBD cross the placenta and displace natural endocannabinoids, which may disrupt fetal brain wiring.
• Mistake: Believing legality implies safety.
  Fix: Legalization reflects social policy, not scientific safety. THC remains potentially neurotoxic to developing brains.
• Mistake: Continuing cannabis use to ease withdrawal symptoms during pregnancy.
  Fix: The risk to the fetus outweighs maternal discomfort. Withdrawal should be managed medically, not through continued use.

Despite widespread legalization, cannabis use during pregnancy and breastfeeding is unsafe. Cannabinoid receptors play a vital role in fetal neural wiring, and exposure to THC or CBD can interfere with this process. Experts urge complete abstinence during pregnancy and lactation to avoid potentially lifelong consequences for the child’s brain development.