As marijuana (cannabis) gains legal status and cultural acceptance state by state, important questions about who should be using the drug are becoming more pressing. Recently, a major medical organization announced its stance on marijuana use during pregnancy or while breastfeeding: It’s not a good idea.
The American Academy of Pediatrics (AAP) is officially recommending that pediatricians advise women to abstain from marijuana use during pregnancy and breastfeeding. Their recommendations are based on a clinical report reviewing the small but concerning body of research suggesting that this practice could potentially interfere with the healthy growth and development of the fetus, infant, or child.
“The main takeaway is that women should not use marijuana throughout pregnancy,” report co-author Seth Ammerman, Ph.D, M.D., clinical professor in the Division of Adolescent Medicine, Department of Pediatrics at Stanford University, tells SELF. “There’s limited evidence, but what evidence is out there says that it could cause adverse consequences to the developing fetus, as well as even further on in infancy and childhood.”
The AAP also recommends abstaining from using marijuana while nursing, although it’s not yet clear if the potential dangers are enough to outweigh the benefits of breastfeeding. (More on that in a bit.)
The AAP’s conservative stance echoes that of the The American College of Obstetricians and Gynecologists (ACOG). ACOG advises pregnant women to avoid marijuana because of the potential impact on neurodevelopment—and the exposure to smoke, in some cases—while acknowledging that it is “difficult to be certain about the specific effects of marijuana on pregnancy and the developing fetus, in part because those who use it often use other drugs as well, including tobacco, alcohol, or illicit drugs.”
The major psychoactive component of cannabis is THC (tetrahydrocannabinol), which can cross into the placenta and into breast milk.
According to the AAP report, there is indeed “limited data” showing that it could be passed to a fetus (including animal studies, like a 1989 study of rats, and a 1987 study of rhesus monkeys. The evidence that THC can pass into breast milk is more recent and definitive.
“Therefore, if women are using marijuana during pregnancy or while breastfeeding, there is a potential to impact the normal functions and development of the fetus or infant,” Laura M. Borgelt, Pharm.D., a professor and associate dean of administration and operations at the University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences, tells SELF. However, how much gets across the placenta, and at what point it may affect the fetus, is not well understood yet.
There are a few reasons why cannabis exposure may be more complicated than exposure to other substances during pregnancy and breastfeeding. Unlike alcohol, for example, which is metabolized and cleared from the body relatively quickly and straightforwardly, the cannabinoids in marijuana (including THC) can linger in the body for weeks after use, Valerie J. Flaherman, M.D., M.P.H., a pediatrician at UCSF Benioff Children's Hospitals, tells SELF.
“The psychoactive components of marijuana are stored in maternal fatty tissue, and so they’re released from that fatty tissue into the maternal bloodstream—and thereby potentially into the [uterine environment] or the breast milk—with a variable pattern, kind of unpredictably,” Dr. Flaherman says. This makes it harder to predict how long THC will be present for, and in what quantities, which also makes it more complicated to study.
The body of research on what cannabis exposure potentially does to a developing fetus, infant, or child is limited. But it still has experts concerned.
“There is increasing evidence that exposure to marijuana during pregnancy could result in adverse outcomes in areas such as attention problems, decreased cognitive function and IQ scores, and decreased growth that may not be seen until childhood or adolescence,” Borgelt explains.
A 2009 analysis of data from the National Birth Defects Prevention Study published in Epidemiology studied links between illicit drug use during the periconceptional period—which spans from before conception to early pregnancy—and birth defects in 10,241 infants with major congenital malformations (with a control group of 4,967 infants without major congenital malformations) born between 1997 and 2003. The research showed that there seems to be a possible association between periconceptional cannabis use and increased risk of an infant being born with anencephaly, a serious birth defect where the child is missing parts of their brain and skull.
But it's important to put the actual numbers in context. Of the 244 infants born with this defect in the study, only 12 of them were born to women who used cannabis during the periconceptional period. (Only 5 percent of the participants reported using illicit drugs during periconception.) Additionally, the researchers found no association between cannabis use and the other 19 types of congenital issues they looked at. "In general, cannabis does not seem to be associated with major congenital anomalies,” they concluded.
A 2017 study published in The Journal of Maternal-Fetal & Neonatal Medicine, on the other hand, found no association between cannabis exposure in-utero and adverse health outcomes as an infant or in early childhood. Of the 1,867 preterm infants included in the study 135 of them had been exposed to cannabis in utero. One limitation of this study, however, is the fact that they did not measure how often the women used cannabis (meaning that the child of a woman who used cannabis only once, for example, would be counted as being exposed).
Because the drug has historically been difficult to study, there are limitations to the existing research. Consider the wide variation in dosage, potency, timing, and frequency of usage that naturally occurs outside the laboratory setting. Another potential weakness is the reliance on self-reporting, which Ammerman says is not the most accurate method—especially when it comes to illegal substances, because people may under-report how often and how much they use. And women who use cannabis may be more likely to use other substances, such as alcohol and tobacco, making it difficult to isolate the effects of cannabis from those other substances, Ammerman says.
For example, the AAP report includes a 2016 meta-review published in BMJ Open that looked at 24 studies and found “infants exposed prenatally to marijuana had a decrease in birth weight […] and a higher likelihood of needing admission to an NICU.” However, most of the studies included in this review did not exclude women using other substances (e.g. tobacco or alcohol).
Another 2016 meta-analysis cited in the AAP report, published in Obstetrics & Gynecology, pooled data from 31 studies to analyze the relationship between marijuana use and outcomes including low birth weight, NICU admission, spontaneous abortion, and preterm delivery. Researchers found that cannabis use during pregnancy was associated with an increased risk for low birth weight and early delivery. However, after adjusting for confounding factors (such as co-occurring tobacco use), they found that “maternal marijuana use during pregnancy is not an independent risk factor for adverse neonatal outcomes.”
And while we know that THC can get into breast milk, it's unclear what effect that could have on a baby.
According to the AAP, “Limited data reveal that THC does transfer into human milk, and there is no evidence for the safety or harm of marijuana use during lactation.” Basically, we know it can pass to an infant through breastfeeding, but we don't know how worried we should be about that.
For starters, it's unclear how long the THC remains in a person's milk. One recent study published in Pediatrics in August showed THC was detectable in the breast milk of 34 out of 54 breast milk samples from 50 cannabis-using mothers up to six days after use.
It's also uncertain how exposure to THC (or other compounds) may affect the child. (And when it comes to other cannabinoids transferring into breast milk, we don’t know much at all.) As the CDC, notes, “data on the effects of marijuana exposure to the infant through breastfeeding are limited and conflicting.”
One challenge is that “most mothers who use while nursing also used in pregnancy, [so] separating out effects of each is also difficult,” Maya Bunik, M.D., M.P.H., pediatrician and Medical Director of the Child Health Clinic at Children’s Hospital Colorado and pediatrics professor at the University of Colorado School of Medicine, tells SELF.
For example, a study published in Neurotoxicology and Teratology in 1990 found that "marijuana exposure via the mother's milk during the first month postpartum appeared to be associated with a decrease in infant motor development at one year of age," even after controlling for the use of other substances (tobacco, alcohol, and cocaine). However, these women also used cannabis in early pregnancy, making the effects of using the drug only while they were breastfeeding impossible to tease out from this study.
Experts are also concerned about the potential for long-term effects from cannabis exposure that may not appear until later in childhood.
The potential neurodevelopmental effects “include problems with learning, behavior control, executive functioning, attention issues, and mental health concerns,” Erica Wymore, M.D., M.P.H., a neonatologist at Children’s Hospital Colorado and professor at the University of Colorado School of Medicine, tells SELF. “The challenge is that these problems occur much later in childhood, rather than in the newborn period.”
For example, the AAP cites one longitudinal study published in 1995. In this study, starting in 1978, researchers followed the children of 84 pregnant women who used cannabis during pregnancy. They demonstrated that, “independent of tobacco and other drugs, marijuana exposure has significant and pervasive effects that are noticeable in children beginning at 4 years of age and continuing into young adulthood," (when compared to standard benchmarks).
This includes issues with language comprehension, memory, and visual/perceptual function at age 6 as well as problems with attention, problem-solving, and analytical skills at ages 13-16. The study is relatively small, though, and demonstrates a correlation, not a causal link.
Another major longitudinal study of 606 children aged 10, published in the journal Neurotoxicology and Teratology in 2004, found that being exposed to marijuana during the first trimester was associated with deficits in reading and spelling scores and lower ratings in performance from teachers. However, this link didn't seem to be based on neurodevelopment issues. Instead, first trimester heavy marijuana exposure was also strongly associated with the child’s self-reported symptoms of anxiety and depression. The authors explained that "the effects of first-trimester marijuana use on achievement were explained entirely by the effects of prenatal marijuana use on the child’s depression and anxiety." That said, it's also not clear whether the exposure to marijuana led to symptoms of anxiety and depression or if other situational factors played a role in both.
The results regarding second-trimester marijuana use were more troubling. Exposure during this period was associated with a higher chance of displaying underachievement (a discrepancy between expected results based on intelligence tests and actual achievement test results) and deficits in reading comprehension (based on achievement test scores) at age 10.
There were some limitations here, too, including the fact that the researchers weren't able to control for a variety of other factors that may have played a role, including the child's social skills and the level of educational support they received from their parents. Additionally, all of the participants were from a low-income sample and only included those who sought prenatal care, so it's unclear to what degree these results would apply to other populations.
So what should breastfeeding moms know about using marijuana?
“It has not been possible until recently in the medical world to study marijuana use, but because of states like [Colorado] where marijuana is now legalized we are starting to put together the picture of exposure,” Dr. Bunik, who is also a member of the Executive Committee of AAP’s Section on Breastfeeding, says. “We need more research to definitively determine THC's effects on babies during pregnancy and breastfeeding and this type of research takes time.”
In the meantime, experts agree that in the absence of better research, pregnant or nursing moms should definitely err on the side of caution to protect the health of their fetus or baby. According to the AAP—as well as the CDC, ACOG, and the Academy of Breastfeeding Medicine (ABM)—your safest bet seems to be not using cannabis at all while breastfeeding.
As Borgelt puts it, “There is no known safe amount of marijuana” for pregnant and nursing mothers. In light of this fact, abstaining from marijuana is “unquestionably the most cautious and appropriate preventive measure a mom can take at this time,” Dr. Flaherman says. “We want to be sure that both the mom and the developing baby are safe and have the best outcome possible,” Ammerman says.
But, while abstinence is advised, a couple of the experts we spoke with believe there isn’t enough definitive evidence at this point to say that a women using cannabis should not breastfeed. “If a mom was using marijuana and breastfeeding, I would first encourage her to discontinue using marijuana and continue breastfeeding,” Dr. Flaherman says. “But if she was unable to discontinue using marijuana, I would not encourage her to stop breastfeeding because the benefits of breastfeeding are known and the risks of marijuana transmitted in breast milk are not yet well known, since they haven’t been well investigated yet.”
Ammerman takes a similar position. “With the limited evidence we have, it looks like the benefits of breastfeeding outweigh the potential for adverse consequences of possible exposure,” he says. ABM echoes the sentiment: “At this time, although the data are not strong enough to recommend not breastfeeding with any marijuana use, we urge caution.”
Borgelt also thinks that the potential positive effects of breastfeeding, even when using marijuana, do outweigh the potential negative effects of not breastfeeding. “But not if marijuana is chronically used or abused,” she emphasizes.
Not everyone falls in this camp, however. Bunik, for one, disagrees. "Even though we would like to believe that breastfeeding can overcome all negative exposures, like to THC, if a mother chooses to use marijuana they should not breastfeed,” she says. “We have no evidence that breastfeeding protects infants from neurodevelopmental effects. And we need to be advocates for babies until we know more."
The other thing you’ll definitely want to do is talk to your doctor.
While legality and reporting laws on substance use vary from state to state and you’ll want to research those beforehand, from a medical standpoint total transparency is still ideal. “Open communication with health-care providers allows for best possible health outcomes for pregnant women and their babies,” Borgelt says. “It’s important to talk to your obstetrician and then your pediatrician about your marijuana use, because that will help them evaluate any problems that occur in the fetus or the infant by having full information about the infant’s exposure,” Dr. Flaherman says.
Being honest with your doctor about your cannabis use—and why you're using it—can also help both of you come up with the best plan to tackle those underlying issues. For instance, if you’re using cannabis to help combat unpleasant side effects of pregnancy, like morning sickness, then be honest with your provider about it so they can help you find safe alternative treatments, Dr. Flaherman says.
And if you’re using to manage your stress, then don’t be afraid to ask for help. “Pregnancy and motherhood are stressful times,” Dr. Wymore says, "and women should be encouraged to find healthy, nonpharmacologic ways to handle this stress to be safe and present caregivers." Dr. Bunik adds, “New mothers may need help because postpartum is usually a stressful time in life.”