By Julie Care, PharmD
Cannabis may seem like an attractive alternative medicine to turn to while pregnant or lactating to help ease common ailments such as morning sickness and stress that often plague expectant or new mothers, however, current evidence should make us think twice if this is the best option for a growing baby. In fact, the medical community recommends against using cannabis while pregnant or lactating as studies have demonstrated that it can have an effect on pregnancy outcomes, the growing baby, and the child’s development over time.
The developing brain and body of a fetus and young baby contain an endocannabinoid system just like an adult brain and body do. This endocannabinoid system plays a role in forming brain circuitry that is important for decision making, mood, and response to stress.1 Its been shown that there is a higher level of CB1 receptors in the fetal brain than the adult brain, and the presence of exogenous cannabinoids (i.e. THC, CBD) along with overstimulation of this system can inflict harmful effects on its development.2 This coupled with the fact that cannabinoids ingested or inhaled by the mother cross the placenta and reach the developing baby’s blood stream as well as enter breastmilk during lactation make it likely to impact this delicate process.
Although research is limited with regards to robust clinical trials in this population, existing evidence of the potential harms have led leading organizations to recommend pregnant and breastfeeding women avoid its use. These organizations include the American Medical Association (AMA), the Center for Disease Control and Prevention (CDC), the America Academy of Pediatrics (AAP), and the American College of Obstetricians and Gynecologists (ACOG). In addition, the U.S. Surgeon General published an advisory in 2019 citing the known risks to developing brains and greater availability of high potency marijuana in several different forms.1 The advisory states that no amount of marijuana use during pregnancy or adolescence is known to be safe, and the safest choice is not to use it.
Some of the potential harms of cannabis use during pregnancy include lower birth weight, higher incidence of the newborn requiring a neonatal intensive care unit (NICU) admission, premature birth, and smaller head circumference at birth. There is also an increased risk of stillbirth. A retrospective cohort study reviewing 12.5 million U.S. births compared neonatal outcomes between mothers reporting cannabis dependence or abuse and those reporting no cannabis use from 1999-2013.4 This study found a significantly increased risk of preterm birth (14.5% vs 7.1%, P<0.0001), intrauterine growth restriction (4.8% vs 1.9%, P<0.0001), and intrauterine fetal demise (1.4% vs 0.6%, P<0.0001) in babies born to cannabis users.4 Additional studies have found similar results in addition to impacts of marijuana use during pregnancy resulting in changes in neurotransmitters and brain biochemistry as well as altered oxygen intake and fetal heart rate.
In addition to these in utero changes, long-term effects of marijuana use during pregnancy have also been demonstrated in studies conducted in young children and early adulthood, including lower cognitive, memory, behavioral, reading comprehension, spelling and math test scores. Other long-term changes found in these children have included greater risk for impulse control issues, hyperactivity and inattention issues.
Despite these findings, marijuana use during pregnancy has increased over the last few decades as demonstrated in recent studies. In a national survey conducted in the U.S. between 2002 and 2017, marijuana use increased from 3.4% to 7% within that time frame.5 Similarly, there was an increase of marijuana use in pregnant women from 4.2% to 7.1% between 2009 and 2016 found in another study conducted at a large healthcare system in California.
After birth, marijuana use in a lactating mother may still negatively impact the baby. The main cannabinoid, THC, is known to transfer into human breast milk and can be detected for up to six days past the last recorded use.1 Decreased motor development was found at one year of age in one study of infants exposed during the first month postpartum, although this was a small study (n=136) with several confounding factors.3 Although there is a lack of robust data in this population, reputable organizations (CDC, AAP, and ACOG) caution against the use of cannabis including CBD products while breast feeding due to concerns for a negative impact on the newborn’s brain development.
Given the negative outcomes observed in young babies, children and young adults it is clear that alternative, safer options should be utilized to treat common pregnancy ailments and marijuana should also be avoided when the mother is breast feeding. There is likely an even greater risk to the pregnancy and the newborn in current times compared to years ago as the potency and availability of marijuana has greatly increased over the last few decades. Pregnant women should be advised of these concerns and warned against all cannabinoid use during pregnancy and lactation. They should consult with their providers to determine the most appropriate alternative course of therapy to manage stress, pain, nausea and other common conditions that may arise during pregnancy.
U.S. Surgeon General’s Advisory: Marijuana Use and the Developing Brain. Aug 29, 2019. Accessed Feb 18, 2021 from: https://www.hhs.gov/surgeongeneral/reports-and-publications/addiction-and-substance-misuse/advisory-on-marijuana-use-and-developing-brain/index.html
Mato S, Del Olmo E, and Pazos A. Eur J Neurosci. 2003;17:1747-54.
Ryan SA, Ammerman SD, and O’Connor ME. Pediatrics. 2018;142(3):e20181889.
Petrangelo A, et al. J Obstet Gynaecol Can. 2019;41(5):623-30.
Volkow N.D., Han B., Compton W.M., et al. JAMA. 2019;322:167-169.
Young-Wolff KC, Tucker L, Alexeeff S, et al. JAMA. 2017;318(24):2490–2491.
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