With the legalization of marijuana showing up on the ballot in increasingly more states, public health organizations are trying to better understand the various effects medicinal and recreational cannabinoid use has on long-term health and neurodevelopment. The lack of specific data in certain areas, such as breastfeeding, is concerning as increased use has been documented in pregnant and breastfeeding women in states where the drug has become legal. To better understand how much marijuana or constituent compounds get into breast milk and how long it remains, researchers at University of California (UC) San Diego School of Medicine conducted a study. Findings from the new study were published in Pediatrics through an article titled “Marijuana Use by Breastfeeding Mothers and Cannabinoid Concentrations in Breast Milk.”

“Pediatricians are often put into a challenging situation when a breastfeeding mother asks about the safety of marijuana use,” explains senior study investigator Christina Chambers, Ph.D., a professor in the department of pediatrics at UC San Diego School of Medicine and director of clinical research at Rady Children's Hospital-San Diego. “We don't have strong, published data to support advising against the use of marijuana while breastfeeding, and if women feel they have to choose, we run the risk of them deciding to stop breastfeeding—something we know is hugely beneficial for both mom and baby.”



In the current study, 50 women who used marijuana either daily, weekly, or sporadically—with inhalation being the primary method of intake—were examined. Researchers detected THC, the primary psychoactive component of marijuana, in 63% of the breast milk samples for up to six days after the mother's last reported use.

Cannabinoids—marijuana's active compounds, such as THC—like to bind to fat molecules, which are abundant in breast milk. This stickiness has suggested that, in women who use marijuana, these compounds can end up in breast milk, raising concerns about their potential effects on nursing babies.

The World Health Organization recommends exclusive breastfeeding for up to six months. Early breastfeeding is associated with a reduced risk of obesity, asthma, and sudden infant death syndrome and with improved immune health and performance on intelligence tests. In mothers, breastfeeding has been associated with lower risks for breast and uterine cancer and type 2 diabetes. Thus, a better understanding of how much of the cannabinoid compounds make it into breast milk and how it affects child development is imperative.

“We found that the amount of THC that the infant could potentially ingest from breast milk was relatively low, but we still don't know enough about the drug to say whether or not there is a concern for the infant at any dose, or if there is a safe dosing level,” Dr. Chambers adds. “The ingredients in marijuana products that are available today are thought to be much more potent than products available 20 or 30 years ago.”

The samples of breast milk used for the study were obtained from mothers who joined the Mommy's Milk Human Milk Research Biorepository at UC San Diego, a program that focuses on looking at the numerous benefits of breast milk at the molecular level. Dr. Chambers and her research team collaborated with the Skaggs School of Pharmacy and Pharmaceutical Sciences at UC San Diego to measure the levels of marijuana in the samples.

The researchers were intrigued by their findings, but understand that much more work needs to be done, not only to determine the long-term impact of marijuana in breast milk for children but more specifically: “are there any differences in effects of marijuana in breast milk for a two-month-old versus a 12-month-old, and is it different if the mother smokes versus eats the cannabis? These are critical areas where we need answers as we continue to promote breast milk as the premium in nutrition for infants,” Dr. Chambers concludes.

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