Too much we don’t know about marijuana use and breastfeeding
More research needed into effects of THC on an infant’s developing brain
Doctors, midwives, psychologists and nurses will have to carefully consider the advice they offer to pregnant and lactating mothers who have chosen to use marijuana in whatever form or for whatever reason.
According to a landmark study from San Diego by Kerri Bertrand and her colleagues, published in last month’s journal Pediatrics, marijuana is the most commonly used recreational drug in breastfeeding women. I like the word “recreate” in this context. One has to pause and break it down: re-create. To me, the word implies that we make again or change what is already there.
But how much do we know about the way cannabinoids recreate the baby’s brain when it is exposed to THC via the mother’s milk? Scientific evidence to answer this important question remained essentially nonexistent, until Bertrand and fellow researchers at La Jolla, San Diego, generated data from volunteers residing in the U.S. and Canada.
The study was very thorough and looked at various ways lactating moms elected to consume cannabis — inhaled, ingested and topical. It also looked at how cannabinoids may change when breastmilk is stored in a frozen format. The researchers simply wanted to quantify cannabinoids in human milk after marijuana use. They used sophisticated mass spectroscopy techniques to quantify levels of four cannabinoids ( 9-Tetrahydrocannabinol also known as 9-THC; 11-hydroxy-9-tetrahydrocannabinol; cannabidiol and cannabinol).
The study investigated 50 breastfeeding women who reported marijuana use between 2014 and 2017. They were recruited all over North America through a variety of sources including social media. 9-THC was measurable in the majority of breastmilk samples — up to six days after the last reported use. The THC concentrations depended on the number of daily uses. The level of THC in breast milk was eight times higher than the mother’s plasma level in some cases, suggesting it is concentrated in the milk at higher levels, probably due to the fat content of the milk. When the babies’ stools were studied, researchers found some babies had higher concentrations of THC metabolites than the mother’s breast milk for reasons that still remain unclear.
At this time, researchers know THC is excreted through feces, but they are unaware as to how long it takes to be completely excreted and if THC, over time, accumulates in the brain where it is stored in fat.
What we do know is THC is highly lipophilic — meaning it loves to hang around where there is fat and the brain is a very fat-rich organ. This raises the possibility that small amounts of THC, with repeated exposures, will accumulate in the developing brain- — a brain which requires optimal nutrition, exposure to a healthy environment where parents read to their babies and avoid screen time until age two.
In the U.S., where marijuana is not yet legal in all states, 36 per cent of women report having used marijuana at some point in their pregnancy and 18 per cent report having used it while breastfeeding.
There is limited Canadian data which will tell us how many women have elected or will elect to use marijuana while breastfeeding — both smoked and edible. Time will tell how diligently Canadian Public Health experts will collect data which may be helpful for research.
Meanwhile, in the face of uncertainty, both the AAP and the American College of Obstetricians and Gynecology encourage clinicians to tell lactating moms to abstain from all cannabis products while breastfeeding.
But what about the lactating mother who uses these chemicals for medical reasons? Would it be better for her to use a formula to nourish the baby? Will the benefits of breastfeeding be “wiped out” by the adverse effects of THC on the baby’s developing brain?
Longitudinal research done in the 1980s and 1990s by Astley et al at a time when THC concentrations in marijuana was one-third of what they are today, suggest that psychomotor and neurodevelopmental deficits exist in infants exposed to THC.
While many questions remain unanswered, I predict that the tax dollars generated in Canada by the legalization of marijuana will be insufficient to pay for medical care of babies whose brains were exposed to a chemical toxin such as THC.
There are ethical conundrums to consider still. If we can legislate that children are not to be exposed to second-hand smoke in a confined space — such as a vehicle with the windows closed — can we legislate any other laws to protect a baby’s developing brain from toxins?
For now, it is wise to err on the side of caution, especially when current concentrations of THC levels in marijuana are three times higher than they were some decades ago.