Is it safe to use weed while breastfeeding?

Yes, weed does gets into breastmilk, but there's been little research on how marijuana may impact a baby. Here's what we know so far.

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After long days of breastfeeding, diapering and soothing her baby, Evelyn Lee* was ready for some mommy time. So after putting baby Sophia* to sleep for the night, she would select a marijuana bud from her stash, load her vape and take a few puffs. Her body would relax, her mind would slow down and she would finally feel like herself again. She’d listen to music as she stretched on her yoga mat and then do crafts for a couple of hours.

“Getting a little buzz is really pleasant and a great mental relief and release. It’s like turning off all the noise of the day,” says Lee. “As much as I love being a mom, it’s what allows me to disconnect from that experience for a couple of hours.”

Woman’s fingers rolling a jointIs it safe to use weed during pregnancy? After giving up pot during pregnancy due to concerns that it could harm her baby, Lee had been eager to return to her weekly ritual postpartum. Research shows that using pot during pregnancy may lead to poor outcomes, including low birth weight and long-term neurodevelopmental effects on the child, though the evidence is not conclusive. But studies on the risks during breastfeeding are much more scant, and Lee didn’t find anything suggesting harm when she did research online.

So once she emerged from the fog of the newborn stage and established a sleep routine with Sophia at around three months, she started getting high about once a week, and continued doing so for the next year and a half that her daughter nursed—always in the evening after putting the baby to sleep. Most nights, about two and a half hours after vaping, Lee would sneak into her daughter’s room to “dream feed”—breastfeed without waking the baby—hoping that, since she no longer felt high, the pot wouldn’t affect Sophia.

While the chemicals in marijuana products, including CBD oil, do pass into breastmilk, there’s little science on how it may affect babies, leaving women like Lee guessing about whether or not it’s safe to use. New research is starting to emerge, suggesting some negative effects on breastfeeding moms and babies, but experts are concerned that the upcoming legalization of recreational marijuana in Canada may send a message that it’s safe.

“When we legalize something, there’s that tendency to think it’s not that bad for you,” says Jamie Seabrook, an associate professor in the School of Food and Nutritional Sciences at Brescia University College in London, Ont., who has done a few recent studies on cannabis use during breastfeeding. “Until more conclusive evidence comes out about the effects, I believe that marijuana use during lactation is going to continue to go up.” 

It’s hard to know how many breastfeeding women use marijuana because many are afraid to admit to it, but a 2017 systematic review by Seabrook and his colleagues suggests the rate is anywhere from three to 30 percent, making it the most common recreational drug used during lactation.

Kerri Bertrand, research manager at the Mommy’s Milk Human Milk Research Biorepository at the University of California, San Diego, says breastfeeding women in her program mainly use pot for recreational purposes or to treat pain, anxiety or depression, including postpartum depression. About 88 percent of them use daily, she adds.

Women who are using cannabis for medical reasons should explore alternatives that have been proven safe, ideally before pregnancy, says Jocelynn Cook, chief scientific officer with the Society of Obstetricians and Gynaecologists of Canada (SOGC). “Women should try to cut down as much as they can and talk to their healthcare provider and see if there’s some other support that they can get or some other options,” she says, though she acknowledges that the alternatives may not work as well for some women.

Can weed affect my breastmilk?

When a breastfeeding mom uses weed, some of the more than 400 chemicals in the plant get into her bloodstream and transfer into her milk. A study led by Bertrand, published in the journal Pediatrics in 2018, examined breastmilk samples from 50 women in Canada and the United States who used marijuana and found that 63 percent had detectable levels of tetrahydrocannabinol (THC), the main psychoactive component of cannabis, up to six days after they last used. Only nine percent had detectable levels of cannabidiol (CBD), the primary non-psychoactive component of the drug, which is responsible for many of the medicinal benefits of the plant such as reducing pain, nausea and anxiety.

“THC and CBD bind heavily to fat, and fat is a main nutrient in breastmilk,” Bertrand says. But just because the chemicals are detectable doesn’t mean that they’re harmful. Although, Bertrand says, “we are concerned with THC being psychoactive and how that may influence the child’s brain development.”

Bertrand’s study found that the number of times per day a woman used and the length of time since last use influenced the level of THC. The method by which a woman consumed cannabis also played a role in how much THC showed up in her milk, with inhalation—smoking, vaping or using a bong—leading to higher levels than edibles or topicals. Using a vape, however, might be preferable to smoking because it reduces exposure to the byproducts of combustion and carcinogens. Smoking can also expose babies to secondhand smoke, which can lead to ear and respiratory infections and even sudden infant death syndrome.

According to Bertrand’s study, the amount of THC in breastmilk decreased by about three percent per hour on average, and babies were exposed to about 1,000 times less THC than their mothers. Unlike alcohol, which leaves breastmilk at the same rate as it leaves the mother’s blood, marijuana can accumulate in breastmilk. One report found that there was eight times as much THC in a woman’s milk as there was in her blood.

“It comes down to how much a mom is using and how much that baby is feeding,” Bertrand says. “We just don’t know if there’s any safe level at this point, and we don’t know how it’s influencing infant and child health.”

And while pumping and dumping may help to reduce the chemicals in breastmilk, “it doesn’t seem feasible since THC is staying in the milk for so long,” Bertrand says. “It would be really hard for a mom to pump and dump for, say, six days if she only smoked that one time.”

Can using weed while breastfeeding affect my baby?

The limited knowledge we do have about the effects of marijuana use during breastfeeding on child development come from two small studies from the ’80s and ’90s. One found that marijuana exposure via breastmilk in the first month postpartum was associated with decreased motor development at age one, but there was no effect associated with use in the third month. The other study concluded that using cannabis during lactation had no effect on infant growth or development at age one. But it’s important to note that both of these studies had small samples sizes and were done three decades ago, when pot was an estimated 300 percent weaker than it is today. “Given the potency of marijuana is going up a lot, the negative effects on babies who are breastfed, especially by mothers with heavy use, could be way worse,” Seabrook says.

A study on suckling mice found that pups exposed to a cannabis extract gained significantly less weight than those that were not exposed, and a rat study found that moderate doses of THC influenced brain development and led to lasting neurodevelopmental changes. “Those lasting changes could potentially translate into human studies,” Seabrook says. “One of the concerns is that the THC that babies are exposed to can obstruct the connections of the developing brain and potentially lead to permanent changes.”

THC also affects the quantity and quality of breastmilk by inhibiting the production of prolactin, the hormone associated with milk production, and stimulating or suppressing the release of other hormones connected to the quality of milk. In turn, babies have been found to become sedated and have poor sucking and reduced feeding time, according to a few studies.

Marijuana can have negative effects on the mother, too, which may interfere with breastfeeding and parenting. For example, it can lead to panic attacks, delayed response time, short-term memory problems, dizziness and increased heart rate. Women who use marijuana are also more likely to experience depression. However, the drug is often used to treat depression, and it’s uncertain if marijuana triggers the mental illness or if those with depression are simply more likely to use.

Should I stop using weed while breastfeeding?

With much more research needed to determine what effects marijuana may have on breastfeeding babies, experts are urging moms to take a cautious approach. In a 2018 clinical report, the American Academy of Pediatrics concluded that there is no evidence for the safety or harm of marijuana use during lactation and, as result, nursing mothers should abstain from using the drug. This is in line with the SOGC’s position statement, which says women should be encouraged to abstain from cannabis use during breastfeeding.

But for those who can’t or won’t quit using cannabis, do the benefits of breastfeeding—increased intelligence, improved immune system and mother-baby bonding—outweigh the potential negative effects of breastfeeding while using marijuana? It depends who you ask.

A study of 74 lactation professionals in New England published in 2015 found that 41 percent encouraged women to continue breastfeeding while using cannabis because the benefits outweighed the harms, 44 percent said their recommendations would depend on factors such as the quantity consumed and 15 percent said women should stop breastfeeding if they couldn’t give up pot.

Seabrook says recommendations should depend on quantity consumed, though no safe limit of cannabis during breastfeeding has been established. “We know that breastmilk is the optimal form of nutrition for babies,” Seabrook says. “But based on the limited research that we have, breastfeeding moms should be recommended to limit or cease their use of cannabis because there are concerns with risk to the developing brains of their babies. And caution, I think, always has to come first.”

*Names have been changed.

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