Cannabis use during lactation is a growing public concern, especially as more regions legalize its use. The primary compounds of interest are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). These substances pose a potential risk because they can be transferred from the mother to the nursing infant through breast milk. Understanding how these compounds move into milk and their potential effects on the baby is important for informed decisions about infant feeding.
How Cannabis Compounds Enter Breast Milk
The mechanism by which cannabis compounds enter human milk is linked to their chemical structure. Tetrahydrocannabinol (THC), the main psychoactive component, is highly lipophilic, meaning it readily dissolves in fat. Since breast milk contains a high proportion of fat, THC concentrates there, often reaching levels eight times higher than in the mother’s blood plasma.
The concentration of THC varies based on the mother’s frequency of use and the product’s potency. For regular users, THC can be detected in breast milk for an extended period. The estimated mean half-life of THC for chronic users is about 17 days, with full elimination potentially taking longer than six weeks.
Even after a single use, THC can remain detectable for up to six days. This persistence means the “pump and dump” strategy, effective for substances with a short half-life like alcohol, is ineffective for clearing THC. THC is released slowly over time from the mother’s body fat stores into the bloodstream and subsequently into the milk.
Documented Impact on Infant Development and Health
Exposure to THC through breast milk is a concern because the developing infant brain has a high density of cannabinoid receptors, which THC can activate. Early exposure may disrupt the natural endocannabinoid system, which plays a role in brain development and function. Research indicates that infants exposed via breast milk are also likely to have had prenatal exposure, making it difficult to isolate the effects of lactation exposure alone.
One study using the Bayley Scales of Infant Development found an association between cannabis exposure in the first month of lactation and a decrease in infant motor development scores at one year of age. This psychomotor development index (PDI) assesses fine and gross motor skills. However, other earlier studies involving smaller sample sizes did not find differences in motor or mental development at one year.
Case reports involving infants exposed to high levels of cannabis compounds have occasionally noted symptoms such as lethargy, poor feeding, and changes in sleep patterns. These behavioral changes are attributed to the psychoactive properties of THC. Infants exposed through breast milk have been found to excrete THC in their urine for up to two to three weeks, confirming absorption and systemic exposure.
While the available data suggest a potential link between cannabis exposure and adverse developmental outcomes, robust, long-term human studies are limited. Ethical constraints and confounding factors, such as simultaneous use of tobacco or alcohol, complicate the interpretation of results. Despite these limitations, the potential for long-term neurobehavioral effects on the developing brain remains a primary concern.
Official Health Organization Recommendations
Major medical and public health organizations universally advise against using cannabis while breastfeeding. The American Academy of Pediatrics (AAP) and the American College of Obstetricians and Gynecologists (ACOG) strongly recommend abstinence from all forms of cannabis use. This guidance applies to psychoactive THC, non-psychoactive CBD products, and medicinal use, as no amount has been proven safe for the nursing infant.
These recommendations are based on the confirmed transfer and accumulation of THC in breast milk and the unknown long-term consequences for infant neurodevelopment. Healthcare providers should screen patients for substance use and counsel mothers about the risks of metabolite exposure, encouraging complete abstinence.
The consensus among organizations, including the Centers for Disease Control and Prevention (CDC), is to minimize infant exposure due to the lack of data establishing a safe threshold. The goal is to support the mother in abstaining while continuing to encourage breastfeeding for its known benefits.