Can breastfeeding mothers safely use marijuana?

Marijuana is the third most commonly used recreational drug in the United States after alcohol and tobacco. Medical marijuana is currently legal in 33 states and the District of Columbia. Recreational use is permitted in 11 states and legislative agendas suggest that many more states may soon follow their lead. Surveys estimate that tens of millions of Americans use marijuana products each year, but how many women use marijuana during pregnancy or while breastfeeding is unclear. This isn’t surprising given that many women are reluctant to report marijuana use for fear that it will trigger an investigation by law enforcement or child protective services.

Marijuana in breast milk

Marijuana contains numerous ingredients but among them is tetrahydrocannabinol (THC), a psychoactive compound known for its mind-altering effects. When a breastfeeding mother inhales or ingests marijuana, THC is transferred into her breast milk through her blood. THC’s low molecular weight and high fat solubility facilitate its transfer into human milk and its storage in fatty tissues, including the brain. How much THC passes from the milk into the baby’s blood has yet to be determined.

What are the possible risks?

A three-year (2014-2017) study examined 54 breast milk samples from 50 breastfeeding women who reportedly used marijuana. Eighty-eight percent of the women reported daily use (primarily through inhalation), with some women using marijuana up to seven times a day. There was a significant association between frequency of marijuana use and breast milk concentration. THC was detected in a majority of breast milk samples for up to 6 days after maternal marijuana use. While the researchers did not measure infant blood samples, they estimated that the level of cannabis compounds (THC) ingested via breast milk would be 1000 times lower in nursing infants compared to their breastfeeding mothers.

Even though the level of THC in human milk is thought to be too low to cause immediate effects in the nursing infant, concerns have been raised about long-term effects. In a 2009 review of available data, one study found a link between marijuana use while breastfeeding and delayed motor development in children at age one, but other studies failed to show similar results. Until more data are available, women are urged to consider the possible risks of inhaling or ingesting marijuana while breastfeeding which include:

  • Impaired judgement. Use of marijuana may affect a mother’s judgement or impair her ability to properly care for her baby. Parents should never sleep in the same bed with their infant after using marijuana or drinking alcohol as it may dull your senses and increase the risk of your rolling on top of your child and suffocating her.
  • Secondhand smoke. Inhaling someone else’s marijuana or tobacco smoke causes numerous health problems in infants and children, including more frequent and severe asthma attacks, respiratory infections, ear infections, and an increased risk of sudden infant death syndrome (SIDS).
  • Thirdhand smoke. Marijuana (and tobacco) residue can attach to hair, clothing, furniture, walls, and even your child’s toys. This exposure puts your child at higher risk for SIDS and respiratory conditions such as asthma.
  • Drug potency. Many marijuana studies were done over 10 years ago when THC levels were much lower than they are today. Therefore, the effects on infants and children today may be greater than previously recorded.

As more states vote to legalize marijuana, its use among breastfeeding women will likely increase, giving researchers access to more data on the short- and long-term effects on mothers and their infants. For now, health care providers and organizations have little choice but to caution breastfeeding mothers to avoid marijuana use. Those mothers who choose to use marijuana should consult with their health care providers.

Last updated April 7, 2020

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