Marijuana, also known as cannabis or weed—along with other street names—comprises the shredded leaves, flowers, stems and seeds of the hemp plant Cannabis sativa. Cannabis has been used as a medicinal healing plant throughout the world for thousands of years.1 Hemp seed and oil can be found in supermarkets and cannabis can be smoked in hand rolled cigarettes, vaped, brewed to drink as a tea or eaten (eg baked in biscuits).
Tetrahydrocannabinol (THC) and cannabidiol (CBD)
Compared to commercially made nutritional hemp products, therapeutic cannabis (including the kind that is smoked) has higher levels of an active compound called tetrahydrocannabinol, or THC. While THC is the main psychoactive substance that can make you feel “high” and may have negative side effects2, it is also reported to be helpful for a number of medical conditions3 Cannabidiol (CBD) is another non-psychoactive form of cannabis said to have beneficial properties.
In the United Kingdom (UK) cannabis is classified as a Class B controlled drug under Part II, Schedule 2, of the Misuse of Drugs Act 1971 (MDA 1971).4
Smoking cannabis may affect breathing, heart rate, anxiety, paranoia, and give mood swings.5 Cannabis is often mixed with tobacco therefore creating the same risks as smoking tobacco. It may also be cut with other unknown substances which may be harmful. THC can be measured in the blood within seconds of inhaling it, and the concentration peaks within three to ten minutes of smoking cannabis. THC is known to enter areas of the body with a good blood supply such as the liver, heart, lungs, and breast and eventually accumulate in fat tissue.6
Long half life
Marijuana is said to have a long half life (the time it takes for half the substance to dissipate in the body) of 25-57 hours (halesmeds.com, 2022). The longer the half-life, the longer it takes for the body to eliminate it. A general rule of thumb is that a drug’s concentration becomes negligible after five half lives. However THC may be detected in the body for up to a month after the last use because it is stored in body fat.7
Cannabis and breastfeeding
Does marijuana affect breast milk? How long does THC/marijuana stay in breast milk? Is smoking weed while breastfeeding safe? This article looks at frequently asked questions about the safety of smoking weed while breastfeeding.
Smoking weed while breastfeeding FAQ
Does marijuana affect breast milk?
- THC. THC is secreted into breast milk in small quantities (Cannabis. LactMed. 2022) or small to moderate amounts8. There is currently very little research looking at how this affects the breastfed baby and more studies are needed.
- CBD. Little is known about the transfer of cannabidiol (CBD) into breast milk 9
What does existing research say?
Existing studies on mothers smoking weed while breastfeeding have small sample sizes and various shortcomings in the study designs (Hale, 2022). In addition, the information in older studies may not be relevant as the potency (drug activity) of marijuana is said to have increased from around 3% in the 1980s to 12% in 2012.10 See LactMed’s entry for cannabis for a comprehensive discussion of the research which includes:
- A study in 1982 of two women from Perez Reyes and Wall. One of the mothers reported smoking once a day for seven months and the other reported smoking seven times per day for eight months, both of the breastfed infants were said to have normal development.1112
- Tennes et al didn’t find any significant differences in infants’ growth, mental and motor development at one year of age. The study included 756 participating women who used marijuana prenatally and postnatally, of which only 62 infants were breastfed and only 6 had daily exposure to marijuana.13
- A 1990 paper by Astley and Little 14 found only slight changes in motor development of 68 infants at one year of age where mothers were smoking marijuana regularly. No effect was noted on the infants’ mental development.
- In 2018 Thomas Hale—author of Hale’s Medications and Mothers’ Milk Online and fellow researcher Teresa Baker completed a small study (eight women) on how marijuana affects breast milk. THC was found at low concentrations in breast milk —on average 2.5% of the mother’s dose and because the amount of THC absorbed orally is low (less than one to six per cent), the dose absorbed by the breastfed baby is likely to be very small.15 However the current recommendation in Medications and Mothers’ Milk Online continues to be to avoid using cannabis while breastfeeding (Halesmeds.com, 2022).
How long does THC/marijuana stay in breast milk?
THC/marijuana has a long half life and may accumulate in fatty tissue (see above). LactMed states that the length of time THC can be detected in milk ranges from 6 days to more than six weeks (LactMed, 2022) however the amounts are very small compared to the adult dose (Hale, 2022; Baker et al, 2018) and what these levels mean for the breastfed baby is not clear (see above).
Is smoking weed while breastfeeding safe?
The Academy of Breastfeeding Medicine (ABM), 2015 explains that it is difficult to make recommendations for lactation due to scarce research on the effects of exposure of babies to marijuana via breastfeeding alone and not via pregnancy as well. However regular use of weed (marijuana) is generally not considered safe in pregnancy or lactation.
How does smoking weed while breastfeeding affect a baby?
Smoking weed exposes an infant to inhaling the active components of cannabis via secondhand smoke in addition to ingesting small amounts via breast milk. There is also smoke inhalation and the combined effect of the tobacco (and whatever else) mixed with marijuana16. Djulus et al explains that marijuana smoke has been found to contain more than 150 other substances as well as THC because harmful contaminants can be mixed in to street drugs (Djulus et al, 2005).
Research on how THC exposure via breastfeeding might affect the baby is limited and conflicting, and it is difficult to separate the effects of smoking marjuana in pregnancy from the effects of smoking weed while breastfeeding. Concerns about the ways a baby may be affected by his mother smoking marijuana include:
- Safety issues. A mother may be unable to care for her baby safely if she is affected/high on marijuana (ABM, 2015). After taking marijuana, the mother may fall into a deep sleep and be unable to respond to her baby’s needs (Fisher, 2006).
- Effects on a baby. Although data is limited, cannabis exposure during critical periods of brain development may affect mental and motor development and could make a baby sleepy (ABM, 2015: Halesmeds.com, 2022) .
- SIDS. Smoking around a baby has a number of health risks17 and is a known risk factor for Sudden Infant Death Syndrome (SIDS) (LactMed, 2022). Cannabis shouldn’t be smoked in the vicinity of a baby as they will be exposed to inhaling the smoke (LactMed, 2022). Marijuana use by the baby’s father may increase the risk of sudden infant death syndrome (SIDS) in breastfed infants.18
Official recommendations, who says what?
Current advice from LactMed, the Academy of Breastfeeding Medicine, Thomas Hale (halesmeds.com), and the American Academy of Paediatrics is very similar—that breastfeeding mothers:
- avoid using cannabis
- understand the risks of smoking weed for their baby’s brain development
- know the benefits of breastfeeding
- get help to cut down or stop taking marijuana to reduce their baby’s exposure.
Excerpts from useful documents and resources are copied below including opinions on whether occasional use of marijuana is safe and under what circumstances.
Because of insufficient long-term data on the outcome of infants exposed to cannabis via breastmilk, health professionals’ opinions on the acceptability of breastfeeding by cannabis-using mothers varies. In general, professional guidelines recommend that cannabis use should be avoided by nursing mothers, and nursing mothers should be informed of possible adverse effects on infant development from exposure to cannabis compounds in breastmilk. In addition to possible adverse effects from cannabinoids in breastmilk, paternal cannabis use may also increase the risk of sudden infant death syndrome in breastfed infants. Cannabis should not be smoked by anyone in the vicinity of infants because the infants may be exposed by inhaling the smoke.
Thomas Hale, Ph.D.
In Medications and Mothers’ Milk Online, 2022, breastfeeding medications expert Thomas Hale recommends that with the limited data presently available, cannabis use in breastfeeding mothers should be discouraged.
Academy of Breastfeeding Medicine Protocol
The ABM Protocol on substance abuse recommends counselling mothers to stop or cut down drug use and to inform mothers of both the risks of marijuana and the benefits of breastfeeding.
Breastfeeding mothers should be counseled to reduce or eliminate their use of marijuana to avoid exposing their infants to this substance and advised of the possible long-term neurobehavioral effects from continued use.
American Academy of Paediatrics
Breastfeeding has numerous valuable health benefits for the mother and the infant, particularly the preterm infant. 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. Therefore, women also need to be counselled about what is known about the adverse effects of THC on brain development during early infancy, when brain growth and development are rapid.
What about occasional marijuana and breastfeeding?
When a mother only smokes weed occasionally, the many benefits of breastfeeding—which can lower some of the side effects of smoking—must be weighed against the risks of using the drug and the risks of using formula.
The Academy of Breastfeeding Medicine says:
Counsel mothers who admit to occasional or rare use to avoid further use or reduce their use as much as possible while breastfeeding, advise them as to its possible long-term neurobehavioral effects, and instruct them to avoid direct exposure of the infant to marijuana and its smoke.
Dr Jack Newman, Canadian paediatrician and breastfeeding expert writes:
The tetrahydrocannabinol (THC), the compound in marijuana is very highly protein bound, 99.9% protein bound. Furthermore, if taken by mouth (as might the baby) it is very poorly absorbed from the intestinal tract with only 6 to 20% of it absorbed. With such high protein binding, it is unlikely that significant amounts will get into the milk. But note again, that the “high” the mother experiences could last for a few hours, and so her judgement will also be impaired.
Cannabidiol (CBD), is now used widely as treatment for various medical disorders (medical marijuana) and thus not really a drug of recreation. It has low oral absorption, less than 20% of the orally taken dose, is absorbed.
If a mother is using marijuana occasionally, and is capable of taking good care of the baby, there is no reason to advise formula. There is no evidence that the small amounts present in the milk will harm the baby.
A useful paper by Denise Fisher, 2006 points out that while we have little current evidence of long-term detrimental effects to the baby of smoking weed while breastfeeding, there is well established evidence that artificial milks can have detrimental long term effects. She points out that if the mother decides to formula feed, she will need to consider whether she can afford to buy the formula milk, make up the bottles in clean and sterile conditions and to the right strength—if she is high on drugs. Fisher debates whether formula feeding in such circumstances could be more risky for the baby than breastfeeding. She adds that for occasional use the mother could pump milk beforehand to give to her baby and would be advised to have a responsible adult to care for the baby if she plans to get stoned.
Can marijuana affect hormones or milk supply?
Smoking marijuana may affect blood levels of prolactin—a hormone affecting milk production. LactMed summarises the research and concludes that the effects of long term cannabis use on prolactin are not clear since some studies found lower prolactin, some found no difference and some found really high levels:
Acute one-time marijuana smoking suppresses serum concentrations of luteinizing hormone and prolactin in nonpregnant, nonlactating women. The effects of long-term use is unclear, with some studies finding no effect on serum prolactin. However, hyperprolactinemia [a really high level of prolactin] has been reported in some chronic cannabis users, and galactorrhea [spontaneous milk production] and hyperprolactinemia were reported in a woman who smoked marijuana for over 1 year. The prolactin level in a mother with established lactation may not affect her ability to breastfeed.
What about medical use of marijuana?
Lauwers and Swisher talk briefly about medical use of marijuana, see excerpt:
Medical marijuana is used in Canada, part of the United States, and Europe to treat chronic pain and nausea. Moreover several countries and states in the United States have legalized the recreational use of marijuana. Lactation consultants in these countries may encounter breastfeeding mothers who are using marijuana for medical reasons or recreationally.
In an insightful discussion thread on infantrisk.com, Thomas Hale discusses that if a mother is using marijuana, her baby’s urine can be monitored to check the levels in the baby:
If she ONLY used [marijuana], then I wouldn’t be too concerned about her breastfeeding. I’d simply tell her that it passes into milk easily, and we are going to bring her infant in at one month and do a urine screen on the infant.
There isn’t very much information on how a mother smoking weed while breastfeeding might affect her baby. General advice appears to be that marijuana is contraindicated for a nursing mother because;
- a mother’s ability to care for her baby safely could be affected
- it is a drug of abuse that passes to the baby via smoke and in small amounts via breast milk
- secondhand smoke /smoke inhalation is harmful
- the drug’s profile may have the potential to affect a baby’s developing brain
- street drugs are often mixed with tobacco and/or potentially more dangerous substances giving a combined effect
- a mother may also be taking other more dangerous drugs in other forms—compounding the risk to the baby.
Discussing drug use with your Health Professional will allow them to help and advise you on a safe way forward for you and your baby.