Marijuana remains in breast milk up to six days after use

The researchers at University of California San Diego School of Medicine conducted a study to better understand how much marijuana or constituent compounds actually get into breast milk and how long it remains. It has been published in Pediatrics.

"Pediatricians are often put into a challenging situation when a breastfeeding mother asks about the safety of marijuana use. We don't have strong, published data to support advising against 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," said Christina Chambers, PhD, MPH, principal investigator of the study, 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.

Fifty-four samples from 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 percent 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.

"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," said Chambers, co-director of the Center for Better Beginnings at UC San Diego. "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. Chambers and her research team collaborated with Skaggs School of Pharmacy and Pharmaceutical Sciences at UC San Diego to measure the levels of marijuana in the samples.

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.