Cannabis During Pregnancy and Breastfeeding: Medical Evidence and Safety

What Medical Organizations Recommend

The consensus among major medical organizations is clear and consistent: cannabis should be avoided during pregnancy and breastfeeding. This recommendation applies to all forms of cannabis, including THC, CBD, edibles, topicals, and inhaled products.

• ACOG (American College of Obstetricians and Gynecologists) recommends that obstetricians counsel patients to discontinue cannabis use during pregnancy and lactation. ACOG recommends screening all pregnant patients for substance use, including cannabis.
• AAP (American Academy of Pediatrics) advises against cannabis use during pregnancy, breastfeeding, and adolescence due to potential effects on fetal and infant brain development.
• U.S. Surgeon General issued an advisory in 2019 specifically warning against cannabis use during pregnancy and breastfeeding, citing concerns about fetal brain development and birth outcomes.
• CDC (Centers for Disease Control and Prevention) states that no amount of cannabis use during pregnancy or breastfeeding is known to be safe.

These organizations base their recommendations on the precautionary principle: when potential harm to a developing fetus or infant is plausible based on available evidence, avoidance is recommended even if the research is not yet conclusive.

THC Transfer Through the Placenta

THC is a lipophilic (fat-soluble) molecule that crosses the placental barrier readily. When a pregnant person consumes cannabis, THC enters the bloodstream and passes through the placenta to the developing fetus. Fetal exposure to THC is not the same as adult exposure because the fetal brain is in active development and the endocannabinoid system plays a critical role in that developmental process.

The endocannabinoid system begins functioning early in fetal development and is involved in neural circuit formation, neuron migration, synapse development, and neurotransmitter system maturation. Introducing exogenous cannabinoids (THC, CBD) during these critical developmental windows could theoretically disrupt these processes, though the extent and clinical significance of disruption in humans is still being studied.

Animal studies have demonstrated that prenatal THC exposure can alter dopamine and serotonin system development, affect stress response programming, and influence behavior in offspring. Human research is more limited due to ethical constraints on studying pregnant populations, but observational studies have found associations between prenatal cannabis exposure and lower birth weight, increased NICU admissions, and subtle differences in childhood attention and behavior.

THC Transfer Through Breast Milk

THC is stored in fat tissue and is secreted in breast milk. Because breast milk is high in fat content, THC concentrates in it at levels that can be significant relative to maternal blood levels. Research has detected THC in breast milk for up to 6 days after the last use, and in heavy users, the detection window may be longer.

An infant's liver is immature and less capable of metabolizing THC than an adult liver, meaning THC persists longer in an infant's system. The developing infant brain is also more vulnerable to cannabinoid effects than the mature adult brain.

There is no established safe threshold for THC exposure through breast milk. The AAP advises that breastfeeding mothers abstain from cannabis use entirely. Some practitioners suggest that women who use cannabis and wish to breastfeed should discuss the risks with their pediatrician and make an informed decision that weighs the benefits of breastfeeding against the potential risks of THC exposure.

Potential Developmental Effects

Research on the long-term effects of prenatal cannabis exposure is ongoing. Current findings include:

• Birth outcomes — Some studies have found associations between cannabis use during pregnancy and lower birth weight, premature birth, and smaller head circumference at birth. Other studies have found no significant association after controlling for tobacco use and other confounders.
• Neurodevelopment — The Ottawa Prenatal Prospective Study and the Maternal Health Practices and Child Development Study found subtle differences in attention, problem-solving, and impulse control in children prenatally exposed to cannabis. These effects were more pronounced at ages 3 to 6.
• Adolescent outcomes — Some longitudinal studies suggest associations between heavy prenatal cannabis exposure and increased rates of attention problems, depression, and substance use in adolescence, though causation is difficult to establish.

It is important to note that much of this research is observational and confounded by factors like concurrent tobacco use, alcohol use, socioeconomic status, and stress. Randomized controlled trials are not ethically possible in this population. The available evidence is sufficient for major medical organizations to recommend avoidance but insufficient to quantify precise risk levels.

Morning Sickness and Cannabis

Morning sickness (nausea and vomiting of pregnancy) is one of the most commonly cited reasons pregnant individuals consider cannabis use. Severe morning sickness (hyperemesis gravidarum) can be debilitating and resistant to conventional treatments.

While THC is an effective antiemetic in other medical contexts, its use during pregnancy is not recommended due to the fetal exposure concerns described above. Pregnant individuals experiencing severe nausea should work with their OB-GYN to explore pregnancy-safe antiemetic options including vitamin B6, doxylamine (Unisom), ginger supplements, acupressure, and prescription medications like ondansetron (Zofran) when appropriate.

CBD During Pregnancy

CBD has not been studied as extensively as THC in the context of pregnancy, and the absence of data does not imply safety. CBD also crosses the placental barrier, interacts with the endocannabinoid system, and may influence fetal development through mechanisms that are not yet well understood. The FDA has specifically warned against using CBD during pregnancy.

Until research demonstrates safety, CBD should be treated with the same caution as THC during pregnancy and breastfeeding.

Post-Weaning Resumption

For individuals who used cannabis before pregnancy and wish to resume after breastfeeding ends, there are no lasting restrictions. Once you are no longer pregnant or breastfeeding, cannabis use returns to the same risk-benefit profile as for any other adult. Allow sufficient time after your last breastfeeding session for THC to clear from breast milk if you plan to resume cannabis use while transitioning away from breastfeeding.

Discuss the timing of resumption with your healthcare provider, particularly if you are taking postpartum medications or managing postpartum depression or anxiety.

Support and Resources

If you are pregnant or breastfeeding and have questions about cannabis, substance use, or alternative approaches to symptom management, these resources may be helpful:

• Your OB-GYN or midwife — The most important resource. Be honest about any substance use so they can provide appropriate care without judgment.
• SAMHSA National Helpline: 1-800-662-4357 (free, confidential, 24/7)
• Postpartum Support International: 1-800-944-4773
• MotherToBaby: mothertobaby.org — Evidence-based information about exposures during pregnancy and breastfeeding

Read our Cannabis Responsibility and Harm Reduction guide →