Smoking Weed While Breastfeeding

Marijuana, also known as cannabis or weed, is a drug made from the leaves, flowers, stems and seeds of the hemp plant Cannabis sativa. It can be smoked, for example in hand rolled cigarettes, vaped, eaten (mixed in food or baked in biscuits) or brewed to drink as a tea1. The active component in marijuana is called delta-9-tetrahydrocannabinol, or THC. THC can be measured in the blood within seconds of inhaling it, and the concentration peaks within three to ten minutes of smoking it. THC is known to enter areas of the body with a good blood supply such as the liver, heart, lungs, and breast and it accumulates in fat tissue 2.

Marijuana street names

Marijuana, also known as cannabis or weed, has many more street names. The National Institute of Drug Abuse lists them as follows:

Street names: Blunt, Bud, Dope, Ganja, Grass, Green, Herb, Joint, Mary Jane, Pot, Reefer, Sinsemilla, Skunk, Smoke, Trees, Weed; Hashish: Boom, Gangster, Hash, Hemp

dried marijuana

What does marijuana do to you?

Marijuana can affect mood, memory and thought patterns. It may affect breathing (from smoking), heart rate, affect balance and coordination, cause anxiety, paranoia, depression. If used during pregnancy smoking marijuana might lower birth weight or affect brain development in the foetus. For further reading see

Long half life

Marijuana has a long half life (the time it takes for half the substance to dissipate in the body) of 25-57 hours (, 2018) or even up to four days in chronic users 3. 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 is said to be detected in the body for up to a month after the last use because it is stored in body fat (Djulus et al, 2005; Fisher, 2006).

What does this mean for marijuana and breastfeeding? Does marijuana affect breast milk? Is smoking weed while breastfeeding safe? How long does THC/marijuana stay in breast milk?

Marijuana and breastfeeding FAQ

Does marijuana affect breast milk?

Although there is some uncertainty about long term effects and more studies are underway 4, many reputable sources believe that, marijuana does affect breast milk and breastfed babies are at risk of side effects. Wambach & Riordan, 2015 explain:

Mothers should be advised that all of these psychotropic drugs of abuse [marijuana, heroin, LSD, phencyclidine, amphetamines and more] readily enter milk and that their infants may be at high risk of sedation, apnea, or death if the dose is high enough. Further, all mothers should be advised that regardless of the clinical effect on the infant, their infants will be drug-screen positive for many days, and perhaps weeks, following their use.

Small to medium amounts of THC cross into a mother’s breast milk. Djulus et al estimated a baby receives 0.8% of his mother’s dose/kg. In one study of heavy use (seven times per day for eight months) the levels of marijuana in breast milk were eight times higher than in the mother’s blood 5.

More research needed

There are very few studies that have looked at the long term effects for the baby who drinks breast milk containing marijuana. Of the studies that are currently available Tennes et al 6 didn’t find any significant differences in a baby’s growth, mental and motor development; while a 1990 paper by Astley and Little 7 found slight changes in motor development at one year of age especially where mothers were smoking very frequently. See LactMed (cannabis) for further discussion of the research. The information in these and other similar studies may be out of date as the potency (drug activity) of marijuana is said to have increased from around 3% in the 1980s to 12% in 2012 8 and the studies were not sufficiently designed to rule out all long term effects.

Future plans

Thomas Hale—author of Medications and Mothers’ Milk 2017 and fellow researcher Teresa Baker are carrying out new research on how marijuana affects breast milk 9 to review the current marijuana classification of L4 (Limited data—possibly hazardous) in Medications and Mothers’ Milk Online 2018.

Is smoking weed while breastfeeding safe?

Regular use of weed (marijuana) is generally not considered safe in pregnancy or lactation. However 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.

Official recommendations, who says what?

Current advice from the Academy of Breastfeeding Medicine, Thomas Hale, LactMed and the American Academy of Paediatrics is very similar—to get help to cut down or stop taking marijuana and reduce the baby’s exposure. Excerpts from useful documents and resources are copied below. Opinions on whether occasional use of marijuana is safe and under what circumstances vary slightly (see below).

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.

Thomas Hale, Ph.D.

In Medications and Mothers’ Milk Online, 2018, breastfeeding medications expert Thomas Hale classifies cannabis as “Limited data—possibly hazardous” and says:

While this data poses numerous limitations, and does not directly examine the benefits of breast milk versus risks of exposure to marijuana in milk, cannabis use in breastfeeding mothers should be strongly discouraged at this time. Healthcare professionals should encourage alternative treatment options for maternal health conditions requiring the use of marijuana.


Lactmed has similar advice:

Because breastfeeding can mitigate some of the effects of smoking and little evidence of serious infant harm has been seen, it appears preferable to encourage mothers who use marijuana to continue breastfeeding and reducing or abstaining from marijuana use while minimizing infant exposure to marijuana smoke

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.

How long does THC/marijuana stay in breast milk?

THC/marijuana has a long half life (see above). Based on this alone, it might take 5-12 days to be completely eliminated from the body. However THC is stored in fat tissues for weeks or months and may accumulate in breast milk. How long it stays in breast milk will depend on how often marijuana has been taken and a mother and baby’s metabolism. After occasional use of marijuana, Wambach and Riordan 10 recommend stopping breastfeeding for 24 hours—i.e. pump the milk and throw it away (pump and dump). However Dr Jack Newman, Canadian paediatrician and breastfeeding expert is less cautious for occasional use and says:

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.

Breastfeeding is not currently recommended when marijuana is used frequently, because of the cumulative effect.

Alternative milk

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 “clean” 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.

How does smoking weed while breastfeeding affect a baby?

Smoking weed exposes an infant to inhaling the drug via secondhand smoke in addition to ingesting small amounts via breast milk. There is also the combined effect of the tobacco (and whatever else) mixed with marijuana and smoke inhalation 11. Djulus et al 12 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.

Although research is limited, and although it is difficult to separate the effects of taking marjuana in pregnancy from the effects of smoking weed while breastfeeding (or taking it in another form), researchers have documented the ways a baby may be affected by his mother taking marijuana as follows:

  • Babies may be sleepy, have a poor suck, low muscle tone and potential damage to their developing brain (Garry et al, 2009).
  • Babies should be monitored for sedation, poor weight gain, and potential neurobehavioral or psychomotor delays (medsmilk, 2018) including possible long-term changes in behaviour and mental health 13.
  • Smoking around a baby is a known high risk factor for Sudden Infant Death Syndrome. The ABM, 2015 says there is twice the risk of SIDS for babies exposed to second-hand marijuana smoke. Note also that marijuana use by the baby’s father increases the risk of sudden infant death syndrome (SIDS) in breastfed infants14.
  • THC accumulates in breast milk and babies who are exposed to contaminated milk may excrete THC in their urine for two to three weeks (Garry et al; medsmilk, 2018) and it is also evident in the baby’s stools 15.

Can marijuana impair a mother’s ability to care for her baby?

Yes, marijuana use may impair a mother’s ability to look after her child responsibly thus putting the baby’s safety at risk—independent of the drug exposure issue (LactMed, 2018; 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).

Can marijuana affect hormones or milk supply?

One study found that using marijuana could have a profound effect on the mother’s reproductive system including fertility and milk production, along with influencing her sleep patterns, mood, and metabolism by affecting hormone control16. Chronic use of marijuana can lower prolactin levels—a hormone affecting milk production1718. However, hyperprolactinemia (abnormally high levels of prolactin) has been reported in some chronic marijuana users (LactMed).

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, 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.


The evidence of long term harm to a breastfed baby from their mother smoking weed while breastfeeding has not been sufficiently researched or proven. However, general advice appears to be that marijuana is contraindicated for a nursing mother because;

  • a mother’s ability to care for her baby will likely be affected
  • it is a drug of abuse that passes to the baby via smoke and in small amounts via breast milk and can still be found in their urine weeks later
  • the drug’s profile may have the potential to affect a baby’s developing brain with other undesirable short term effects
  • street drugs are notoriously mixed with potentially more dangerous substances
  • a mother may often be taking other more dangerous drugs as well—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.