Does cannabis cross over into breast milk?

From the Guidelines

Cannabis can cross over to breast milk, and its use is not advised during breastfeeding due to potential adverse neonatal outcomes. According to the American Journal of Obstetrics and Gynecology 1, breastfeeding is not recommended for women with concurrent use of illicit substances, including cannabis. This is because cannabis compounds, such as THC, can pass from the mother's bloodstream into her breast milk, potentially affecting infant development.

Key Considerations

• The amount of cannabis that transfers into breast milk depends on factors like frequency of use, potency of the cannabis, and individual metabolism.
• Medical organizations generally recommend avoiding cannabis while breastfeeding due to concerns about potential negative effects on infant brain development, including possible impacts on cognitive function and motor development.
• If a mother uses cannabis for medical reasons, she should discuss alternatives with her healthcare provider that might be safer during breastfeeding.

Clinical Implications

• There is no established "safe" level of cannabis use during breastfeeding.
• Pumping and discarding milk ("pump and dump") does not eliminate THC from milk once it has entered the mother's system.
• Healthcare providers should counsel women about the risks of cannabis use during breastfeeding and provide guidance on safer alternatives.

From the Research

Cannabis and Breast Milk

• Cannabis use has been shown to result in the presence of cannabinoids in breast milk, with several studies demonstrating that these compounds are detectable in human milk produced by mothers who use cannabis 2, 3, 4.
• The physicochemical properties of cannabinoids allow them to be stored in adipose tissue and easily reach the mammary gland, where they can be secreted in milk 2.
• Cannabinoid receptors are present in adipocytes and mammary epithelial cells, and their activation can modulate fatty acid metabolism, potentially causing changes in milk fatty acid profiles 2.

Detection of Cannabinoids in Breast Milk

• Studies have detected various cannabinoids in breast milk, including Δ-9-tetrahydrocannabinol (THC), 11-hydroxy-Δ-9-tetrahydrocannabinol, cannabidiol, and cannabinol 3, 4.
• The concentration of THC in breast milk has been shown to be measurable up to 6 days after maternal marijuana use, with a median concentration of 9.47 ng/mL 3.
• The number of hours since last use, number of daily uses, and time from sample collection to analysis have been identified as significant predictors of log THC concentrations in breast milk 3.

Frequency of Cannabis Use and Breast Milk

• Frequent cannabis use has been associated with higher THC concentrations in breast milk, with one study showing that the median breast milk THC concentration increased from visit 1 to visit 2 by 30.2 ng/mL 4.
• Breastfeeding mothers who use cannabis frequently have been shown to increase their use in the early postpartum period, with a median of 17 instances of cannabis use in the last 7 days at 2 weeks postpartum and 23 instances at 2 months postpartum 4.

Clinical Recommendations

• Women who use cannabis during lactation should be advised to abstain from cannabis use or reduce consumption if abstinence is not possible, and to avoid breastfeeding within 1 hour of inhaled use to reduce exposure to the highest concentration of cannabis in breast milk 5.
• Further research is needed to determine the impact of cannabis use on infant neurodevelopmental outcomes beyond the first year of life, as well as to evaluate infant exposure to cannabinoids via breast milk and effects on infant health 5, 4.