Is Cannabis safe while breastfeeding?

Here is what NIH LactMed, the U.S. National Library of Medicine's authority on medicines and breastfeeding, reports about Cannabis. This is a summary of that source — not our own verdict.

Effects on the breastfed infant

Twenty-seven mothers reported smoking marijuana during breastfeeding. Twelve of them smoked once a month or less, 9 smoked weekly, and 6 smoked daily. Six of their infants were compared at 1 year of age to the infants of mothers who did not smoke marijuana during pregnancy or breastfeeding. No differences were found in growth, or on mental and motor development.[ 4 ] Sixty-eight infants whose mothers reported smoking marijuana during breastfeeding were compared to 68 matched control infants whose mothers did not smoke marijuana. The duration of breastfeeding varied, but the majority of infants were breastfed for 3 months and received less than 16 fluid ounces of formula daily. Motor development of the marijuana-exposed infants was slightly reduced in a dose-dependent (i.e., number of reported joints per week) manner at 1 year of age, especially among those who reported smoking marijuana on more than 15 days per month during the first month of lactation. No effect was found on mental development.[ 3 ] A small, case-control study found that paternal marijuana smoking postpartum increased the risk of sudden infant death syndrome, implying adverse effects from non-breastfeeding exposures, such as second-hand smoke, or factors. In this study, too few nursing mothers smoked marijuana to form any conclusion.[ 32 ] A study of women taking buprenorphine for opiate substitution during pregnancy and lactation found that 4 of the women were also using cannabis as evidenced by positive urine screens for THC between 29 and 56 days postpartum. One was also taking unprescribed benzodiazepines. One infant was exclusively breastfed and the other 3 were mostly breastfeeding with partial supplementation. Infants had no apparent drug-related adverse effects and showed satisfactory developmental progress.[ 33 ] Fifty women who reported using cannabis in the prior 14 days donated milk samples for analysis of THC and its major metabolites. THC was detectable in 66% of the samples and below

Effects on milk supply

Acute one-time marijuana smoking suppresses serum concentrations of luteinizing hormone and prolactin in nonpregnant, nonlactating women.[ 38 - 40 ] The effects of long-term use is unclear, with some studies finding no effect on serum prolactin.[ 41 - 43 ] However, hyperprolactinemia has been reported in some chronic cannabis users,[ 44 - 46 ] and galactorrhea and hyperprolactinemia were reported in a woman who smoked marijuana for over 1 year.[ 46 ] The prolactin level in a mother with established lactation may not affect her ability to breastfeed. Of 258 mothers who reported smoking marijuana during pregnancy, 27 who had smoked marijuana during breastfeeding were followed-up at 1 year. No difference was found in the age of weaning between these mothers and 35 who reported not smoking marijuana during pregnancy or breastfeeding.[ 4 ] The US state of Colorado legalized medical cannabis in 2001 and recreational cannabis in 2012. A cross-sectional survey conducted in Colorado in 2014 and 2015 found that both prenatal and postnatal cannabis use were associated with a shorter duration of breastfeeding. Among women who reported using cannabis during pregnancy, 64% breastfed for 9 or more weeks compared with 78% of women who did not use cannabis during pregnancy. Among women who reported postpartum cannabis use, 58% breastfed for 9 or more weeks compared with 79% of women who did not use cannabis postpartum. Both differences were statistically significant.[ 47 ] A study using a database of 4969 postpartum women found that those who reported using marijuana were more likely to smoke cigarettes, experience postpartum depressive symptoms, and breastfeed for less than 8 weeks.[ 48 ] Tobacco smoking is known to decrease the duration of breastfeeding, so the effect of marijuana is not clear. Most of the women who smoked marijuana postpartum also used it during pregnancy. Among a group of 14 women who used cannabis postpartum by inhalation, lactose levels were higher in the milk

Levels in milk

The main active psychoactive component of cannabis is delta-9-tetrahydrocannabinol (THC), although it also contains other active compounds. THC is very fat soluble and persistent in the body fat of users and slowly released over days to weeks, depending on the extent of use. Maternal Levels. Two women who smoked marijuana daily while nursing had their randomly collected milk analyzed. One mother who reported smoking marijuana once daily had a milk tetrahydrocannabinol concentration of 105 mcg/L; other metabolites were below the level of quantification. The second mother who reported smoking marijuana 7 to 8 times daily had a milk THC concentration of 340 mcg/L; the metabolite 11-hydroxy-THC was found in a concentration of 4 mcg/L and 9-carboxy-THC was below the level of quantification. A milk sample that was collected 1 hour after smoking marijuana contained 60.3 mcg/L of THC, 1.1 mcg/L of 11-hydroxy-THC and 1.6 mcg/L of 9-carboxy-THC.[ 18 ] One source used data in this case to estimate that the infant receives about 0.8% of the maternal weight-adjusted dosage of THC.[ 19 ] However, a poorly characterized assay was used that might not be accurate and the portion of milk (i.e., foremilk versus hindmilk) that was collected by the mothers was not stated. This is important because of the high fat solubility of THC. A woman who admitted to smoking cannabis (amount not stated) donated milk for analysis at an unknown time after the previous use. THC was present in a concentration of 86 mcg/L and 11-hydroxy-THC was present in a concentration of 5 mcg/L; 11-nor-carboxy-9-tetrahydrocannabinol was not detected.[ 20 ] Eight exclusively nursing women who were 3 to 5 months postpartum and reported previous or current cannabis smoking were studied. After 24 hours of abstinence, each smoked a 100 mg of a standardized cannabis containing 23.18% THC. The product was smoked over 10 to 20 minutes from a glass pipe until it was fully consumed. Milk was pumped before smoking and at 20 mi

Source: NIH LactMed (National Library of Medicine).

Educational summary of an authoritative source — not medical advice. Never start, stop, or change a medicine while breastfeeding without confirming with your doctor.