Milk and Marijuana: “First Do No Harm”

Dr. Stellawagen speaks at San Diego County Breastfeeding Coalition meeting.

When California voters approved Proposition 64 and legalize marijuana last year, the basic idea was simple: a majority of people in the state believe that adults should be able to consume marijuana if they feel like it, just like a glass of wine at 5 o’clock. But how about pregnant and/or breastfeeding women? Shall we tell mothers not to breastfeed if they use marijuana?

According to Dr. Lisa Stellawagen (MD, FAAP) of UCSD Medical Center, It’s complicated. Marijuana usage during pregnancy and breastfeeding is an emerging public health problem. At a recent San Diego County Breastfeeding Coalition meeting, Dr. Stellawagen said that THC use is common in pregnancy. Survey shows that 10.9% of pregnant women used Cannabis in the past year. 

In fact, it’s hard for medical staff to know how many mothers actually used Cannabis because self report is not accurate. A 1993 study tested 7470 pregnant women in five centers from 1984 to 1989. All women were asked about drug use and tested by serum analysis. While 31% of the women were confirmed with serum testing, only 11% of them admitted to use marijuana.

Currently we do not have good quality evidence that THC use is bad for infant. Fetal effects of prenatal Marijuana exposure includes small decrease in growth, double increase in stillbirth, but there is no association with birth defects, and the risk of prematurity is unclear. As for neurodevelopment, study found inconsistent effect on newborn behavior.

We do not have good quality evidence that THC use in lactation causes poor outcomes, either. A 1990 study looked at maternal marijuana use during lactation and infant development in one year. Researchers compared one year developmental testing with days of postnatal exposure if breastfeeding, and found that infant’s daily exposure to marijuana in the first month was associated with a 14% decrease in Bayley motor scores, but metal scores were not affected.

We don’t even know how much THC gets into the milk when mother uses marijuana. A 1982 study found that after using THC for one day, there were 105 mcg of THC detected and after using seven days, there were 340 mcg of THC detected per liter of maternal milk. But there was no metabolite detected in infant urine.

That says, before we tell mothers not to breastfeed, we should be sure the risk outweighs the benefit. Benefits of breastmilk for the neonate is of specific significance to the illicit drug exposed infant. Breastfeeding reduces SIDS, decreases risk of neglect, has neurodevelopment effects. Breastfed preterm infant has less NEC, less infection, and better neurodevelopment outcomes.

We do know that THC does get into the baby and mother’s milk, though. So instead of "do not breastfeed if you're using THC," we should tell mothers “do not use THC when you’re pregnant or breastfeeding.” What if mothers are using THC? Dr. Stellawagen suggested, “Others should be available to care for your baby if you use THC. And if you use THC, smoke outside and use a ‘smoking jacket’ to minimize baby exposure.”​

*This is an original post for San Diego County Breastfeeding Coalition by To-wen Tseng.