Many states have legalized marijuana and its use among pregnant women is making headlines. What happens when those pregnant women give birth and decide to breastfeed? Women who use marijuana (the leaves and flowers of the cannabis plant) to alleviate pregnancy-induced nausea or the frequent vomiting associated with hyperemesis gravidarum – HG – may stop using it once their babies are born and symptoms subside. On the other hand, women who find it helps with anxiety or use it medicinally for pain relief find themselves in a tough spot.

At this time marijuana is a Schedule 1 drug, in the same category as heroin. In Colorado, where marijuana is legal both medicinally and recreationally, a fact sheet for healthcare providers urges them to advise breastfeeding women to abstain from using marijuana based on recommendations by the American Academy of Pediatrics.

With little peer-reviewed research on the topic and plenty of stigma around it, many women are hesitant to discuss it with their healthcare providers. A Massachusetts mom I spoke with, who requested anonymity, says she used marijuana about once a month prior to becoming pregnant. Though she seldom smokes while breastfeeding, she would never tell her doctor about her marijuana use, explaining, “I think he would be judgmental about my choice.”

Lea Grover is one mom who speaks openly about marijuana. She calls it her “anti-anxiety drug of choice,” stating that she prefers it to Xanax because it lacks the side effects. Blogger Jeanna Hoch takes it a step further, admitting she uses cannabis daily and did so during her pregnancies and while breastfeeding. She proudly reports her older child suffered no apparent adverse effects; in fact, he was placed in the Highly Gifted and Talented program in first grade.

I interviewed Mary Lynn Mathre, RN, MSN, CARN, founding member and past president of the American Cannabis Nurses Association and president and co-founder of Patients Out of Time. According to Mathre,“it’s safe for breastfeeding moms to use cannabis under most circumstances, but especially if the mother has health problems and needs cannabis for symptom relief.” Mathre advises breastfeeding moms to choose a strain with a lower concentration of THC, the psychoactive component of the cannabis plant. THC concentration can vary widely.  ranging from less than 0.2% to over 20%.

According to Lauren Katz, a sales representative for a Colorado-based cannabis company, dispensaries are required by law to label each product’s THC content. She advises talking to your budtender to determine the right amount for you. Meanwhile, if marijuana is not legal in your state, it’s challenging to determine the concentration of THC. Additionally, there’s the risk that marijuana purchased illegally is laced with other illicit drugs.

Although the research on the effects of THC on infants is very limited, it is known that THC has a long half-life. It is stored in the mother’s fat tissues for weeks, or even months and the urine of infants exposed via breast milk may test positive for marijuana for up to three weeks.

Though limited, some data suggest that exposure to marijuana via breast milk poses no risks for babies. Tests performed on infants up to one-year-old in a 1990 study from Neurotoxicology and Teratology reported no adverse effects on the development of infants who were exposed to marijuana via breast milk at three months old.

A 1985 study published in the NIDA Research Monographs found no significant differences between the age at which infants weaned of mothers who used marijuana while breastfeeding versus those who didn’t. This suggests marijuana didn’t affect the mothers’ milk supply. Additionally, comparisons of measures on infants’ growth, cognitive, and motor skills revealed no differences between infants’ whose mothers reported daily marijuana use versus those who abstained.

A 2001 study in Archives on Pediatrics and Adolescent Medicine found no association between maternal marijuana use and SIDS.

In light of the scant research, the medical establishment advises women to abstain from marijuana while breastfeeding. Groups including La Leche League,  AAP,  and the  American Congress of Obstetricians and Gynecologists agree that no amount of marijuana exposure is safe for infants. While much remains unknown, we know that both secondhand smoke and a mother’s impaired ability to care for her baby while high, are contraindications for using marijuana while breastfeeding.

Some studies support recommendations that breastfeeding women abstain from using marijuana.

A 2013 review in Obstetric Gynecological Survey states that the current evidence suggests mild effects of heavy marijuana use by lactating mothers on their children’s development and that “these effects are not sufficient to warrant concerns above those associated with tobacco use.”

The same 1990 study that identified no adverse developmental outcomes for infants exposed to marijuana via breast milk at three months of age, found that infants exposed to marijuana via breast milk in their first month of life demonstrated decreased motor development at 12 months.

According to a University of California San Diego Medical Center paper, marijuana increases carboxyhemoglobin levels, limiting the blood’s oxygen-carrying capacity.

While the risks of marijuana exposure to babies via breast milk are not totally clear, breast milk is known to be beneficial for babies. This is why some healthcare providers discourage women from using marijuana while breastfeeding but don’t necessarily tell women to stop breastfeeding if they can’t abstain.

A 2015 University of California San Diego Medical Center paper strongly recommends breastfeeding women not use marijuana or expose their babies to secondhand smoke. In that same paper, the authors acknowledge the protective effect of breast milk and recommend that if a mom doesn’t stop using marijuana, that she continue to breastfeed, and that she make sure someone else is available to take care of her baby while she’s intoxicated.

Similarly, a 2015 survey of lactation professionals found 44% of respondents made recommendations on breastfeeding and marijuana on a case-by-case basis, depending on the severity of use. Meanwhile, 41% reported recommending breastfeeding even if the mother continues to use marijuana, as the benefits outweigh the risks. Only 15% said they’d recommend a woman cease breastfeeding if she could not stop using marijuana.

To confuse matters further, guidelines published in Breastfeeding Medicine state, “abstaining from any marijuana use is warranted,” and also that,  “although the data are not strong enough to recommend not breastfeeding with any marijuana use, we urge caution.”

The only thing we know for sure is there is a dearth of evidence. But if the trend toward legalization continues, moms and health professionals may just start demanding answers.