THC from Marijuana Can Linger in Breast Milk for 6 Weeks

Tetrahydrocannabinol (THC), the psychoactive ingredient in marijuana, can remain in breast milk for up to six weeks. Jordan Siemens/Getty Images

New research finds that tetrahydrocannabinol (THC), the psychoactive ingredient in marijua…

Tetrahydrocannabinol (THC), the psychoactive ingredient in marijuana, can remain in breast milk for up to six weeks. Jordan Siemens/Getty Images
  • New research finds that tetrahydrocannabinol (THC), the psychoactive ingredient in marijuana, can remain in breast milk for up to six weeks.
  • Health experts suggest that women who use cannabis should stop long before pregnancy.
  • Studies over the past decade have suggested that THC passed on to babies can trigger learning and attention issues, impulse control, and even depression.

A study published in JAMA Pediatrics on March 8 found that tetrahydrocannabinol (THC), the psychoactive ingredient in marijuana, remains in breast milk for up to six weeks.

The study suggests that could be harmful to infants.

“The American Academy of Pediatrics (and other) medical organizations all recommend that women should abstain from using marijuana during pregnancy and lactation,” Dr. Maya Bunik, senior investigator, medical director of the Child Health Clinic and the Breastfeeding Management Clinic at Children’s Colorado and professor of pediatrics at the CU School of Medicine, told Healthline.

Of the 394 women screened, 25 were enrolled, and 7 abstained from marijuana use for the study's duration.

They gave birth between Nov. 1, 2016, and June 30, 2019. Researchers found that residual THC remained in their breast milk for up to six weeks.

Bunik said the new findings suggest that expectant mothers or those who are trying to conceive should abstain from using cannabis long before pregnancy.

Bunik said she and her team took on the study after noticing that, with legalization, more women were reporting THC usage during pregnancy.

The women in the study were inhaling THC for the most part to relieve stress or pain or to help with sleep.

“With no data,” many hospitals have been suggesting that mothers should abstain from using cannabis for two weeks before nursing. Bunik, however, felt concrete data was needed.

“We wanted to determine the amount of time a mom would have to abstain … [from using THC] before starting direct nursing,” she said.

THC can impact child development

Studies have long hinted that THC passed on to a baby can be damaging.

Studies over the past decade have suggested THC passed on to babies can trigger learning and attention issues, impulse control, and even depression.

That residual THC remains in breast milk for six weeks is notable, Bunik said, because it shows that two weeks is not long enough and hints that the best option is abstinence from THC while pregnant and nursing.

Medical professionals may need to remind pregnant and nursing mothers of the risks, too, since legalization has muddied some understanding of it.

Bunik noted that some women might interpret cannabis use during pregnancy as safe “just because it became legal.”

She added, “We used to think that alcohol and tobacco were safe in pregnancy, but now we know better.”

There’s a growing need for greater education

Dr. Scott Chudnoff, chair of the  Department of OB/GYN at Stamford Health in Connecticut, said there has been an increase in questions from women about the topic.

“Legalization of cannabis has been driving a large amount of discussion regarding its impact during pregnancy, breastfeeding to both the mother and infant,” Chudnoff told Healthline.

“While the current literature out is very sparse of what has been studied, there are definite concerns of its impact on neurodevelopment of the fetus,” he said.

Chudnoff suggested that women who use THC to help with sleep or treat conditions such as anxiety should ask their doctor about safe alternatives while pregnant and through the nursing phase.