Marijuana is the most commonly used illicit drug during pregnancy. From 2002 to 2014 the prevalence of self-reported, past month marijuana use among US adult pregnant women increased from 2.4% to 3.9% (1). Currently, about 1 in 20 women in the US report using marijuana while pregnant (2). The major component in marijuana, THC can easily be passed by maternal circulation, into the placenta, and then into the fetus. Marijuana can be detected in the umbilical cord, neonatal urine, and meconium (first feces of the newborn). These endocannabinoids can impact neurodevelopmental processes, early neural stem cell survival, as well as neuronal connectivity and synaptic function– or in other words, how easily the brain can send signals to other parts of the body. THC is also secreted is breast milk and can accumulate in high concentrations. (1)
Recent studies have shown that exposure to cannabis during pregnancy increases risk of spontaneous abortion/miscarriage, shorter gestation period (premature birth), and low birth weight in infants.
What is the endocannabinoid system?
The endocannabinoid system is a part of the body’s immune system. The communication of this system is focused on keeping the body in a homeostatic state. These pathways are controlled by our own internally produced cannabinoid and cannabinoid receptors. Yes! We produce our own cannabinoids, these are called endocannabinoids. The two most common endogenous cannabinoids are Anandamide and 2AG. Phytocannabinoids are found in plants, the most common found are in marijuana (Cannabis Indica) and hemp plants (Cannabis sativa).
So how does the system work? Cannabinoids (messengers of the system) are created from fat cells within the postsynaptic neuron. They are then released backwards to the presynaptic neuron where they then attach to receptors CB1 and CB2. This system is backwards compared to the release of neurotransmitters. Neurotransmitters are released from a presynaptic cell and travel to attach on the receptors of a nearby neuron- or the postsynaptic cell.
Cannabinoid receptors are located throughout the body- including the brain and endometrium. CBD, CBN, and THC have certain receptors that each bind to. These receptors are part of the endocannabinoid system which impacts physiological process. This can affect pain modulation, memory, appetite, anti-inflammatory effects, and other immune system responses. This system comprises two types of receptors- CB1 and CB2.
CB1 receptors are found primarily in the brain and central nervous system. These receptors are responsible for modulating the perception of pain. These receptors are highly concentrated within the hippocampus (memory, emotion, and learning), cerebral cortex (higher area of thinking- separates us from animals), cerebellum (balance and motor skills), hypothalamus (appetite), and the amygdala (emotions). CB2 receptors are located in the peripheral organs, especially cells associated with the immune system.
Tetrahydrocannabinol (THC) will bind to CB1 receptors, this is why it is considered the psychoactive part of the plant. It increases activity in areas that have high amounts of CB1 receptors. Cannabinol (CBN) will attach to CB2 receptors, it is non-psychoactive and can be used as an analgesic. Cannabidiol (CBD) doesn’t directly bind to the CB1 or CB2 receptors. It influences different chemical reactions and affects different brain receptors like the vanilloid receptor. This receptor is responsible for perceiving pain, regulating body temperature, and inflammation. It can also affect the 5-HT serotonin receptor which is related to anxiety, addiction, appetite, sleep, and nausea. It is thought to balance the psychoactive effects that THC produces.
Can CBD and THC affect a baby in utero? Yes!
Maternal exposure to THC, CBN, and/or CBD can alter endocrine functions as well as concentration of brain biogenic amines (4). Biogenic amine neurotransmitters include: dopamine, norepinephrine/noradrenaline, and epinephrine/adrenaline, histamine, and serotonin (5). Dopamine plays a major role in motivation and motor skills, norepinephrine is released during stress and regulates blood pressure and heart rate, epinephrine is also released during stress and can increase heart rate, blood pressure, and muscle strength (5). Histamine is involved in the inflammatory response and is released during allergic reactions. Serotonin regulates mood, appetite, digestion, and memory. Deficiencies in serotonin can be linked to depression (5).
One animal study found that prenatal exposure to CBN resulted in significant reductions in plasma FSH and LH in adulthood (4). FSH and LH are responsible for stimulating ovulation in females. These researchers suggested that CBN exposure has consistent suppressive effects on pituitary gonadotropin release. Prenatal exposure to THC showed decreased testosterone levels in males when they reached adulthood, suggesting that THC is capable of altering the sensitivity of testis to gonadotropic stimulation. CBN and CBD altered levels of several neurotransmitters including: norepinephrine, dopamine, 5-HT and 5-HIAA (precursors to serotonin) (4). This study suggests that prenatal exposure to either the psychoactive or non-psychoactive components of marijuana can lead to long term changes in neuroendocrine and reproductive functions in males, and these effects may not be apparent until later in life (4).
Another study measured the effects that THC may have on the developing brain (6). Approximately 1⁄3 of THC can pass through the placental barrier upon marijuana consumption during pregnancy. Prenatal exposure to THC may lead to long lasting developmental issues of the nervous system (6). This can affect areas of the brain like the cerebral cortex (frontal lobe), which can lead to problems like ADD, memory problems, anxiety, and depression (6).
Published in the EMBO Journal, children who were exposed to cannabis in utero presented with permanent neurobehavioral and cognitive impairments (7). THC can bind to cannabinoid receptors in the developing fetal brain, leading to disrupted neuron signaling (7). Constant exposure to THC can have a debilitating effect on the CB1 receptors and can actually “rewire” pathways in the brain. Exposure also involves disruption of synapses (neurons communicating to one another) in the baby following pregnancy. This disruption can be lifelong as properly function synapses are critical for highly ordered executive functions. Abnormal synaptic organization could lead to increased incidence of schizophrenia, depression and addiction (7).
There is a lot of research that measures the effects that THC has on the developing fetus, but unfortunately there isn’t a lot of research on what effects CBD use during pregnancy may have. However, in a study published in the American Journal of Obstetrics and Gynecology, it was found that CBD consumption could affect the placental barrier (8). By enhancing placental barrier permeability, the fetus has a greater chance of being exposed to xenobiotics (foreign/harmful substances) that could potentially endanger the developing fetus (8).
Where does CBD and THC come from?
Since CBD and THC products are not regulated by the FDA, there are no standardized definitions of what is a high/low CBD/THC product (9). Medical Marijuana products are typically high in THC but contain a range of cannabinoids. “High-CBD” products are typically higher in CBD than medical marijuana products, but some of these products may still contain levels of THC ranging from 0.3%-0.5% depending on the state law (9). The controlled substance act (CSA) does not define hemp, but exempts certain parts of it including: stalk, fiber, and sterilized seeds from the definition of marijuana (9). However, if CBD is extracted from any part of the plant, including the “exempted parts,” it is still considered marijuana and in Schedule I drug category. Essentially, this is an “exception to the exemption.” The whole hemp plant (with roots in the ground) is defined as marijuana under the CSA (9). Due to its ratio of 10:1 CBD:THC ratio, this seems like a very CBD heavy plant. However, hemp plants are not as high in CBD (only 2-4%) as commonly thought, meaning the ratio above, is somewhat misleading. This shows that true CBD-rich (>12%) plants exist, but they will also contain > 0.3% THC. The plant must be put through a purification process to produce crystalline CBD (9).
Is CBD and/or THC consumption/application safe during pregnancy?
There are a lot of websites that give varying information as to whether or not marijuana is safe to use during pregnancy. THC should absolutely not be consumed during pregnancy, it can have detrimental effects on the neurodevelopment of the fetus, affect neurotransmitter pathways, as well as alter the endocrine system. CBD has not been as well researched, but studies have shown that it can enhance placental barrier permeability (allowing xenobiotics to cross) as well as having an effect on the endocrine system- which can persist into adulthood. Because CBD and THC products are not legal in all 50 states, and is not regulated by the FDA, this can pose some problems when purchasing CBD and/or THC products. The FDA has released a statement to firms that market unapproved new drugs that contain CBD. The FDA tested some of their products and found that a significant number of companies did not contain the amounts of CBD that they claimed. The FDA warns consumers the risk of purchasing these products.
Many of the most common symptoms that occur during pregnancy including: fatigue, morning sickness and pain can be treated naturally. There are many safe and effective treatments that can be given to the mother to alleviate some of these symptoms. Testing may be considered to determine that fatigue isn’t due to a low functioning thyroid, or morning sickness due to food sensitivities. Stretching, yoga, meditation and chiropractic care have also been shown effective at decreasing pain and stress levels in pregnant females.
Based on the research, legality, and still unknown risks that CBD and THC may pose to a developing fetus, I would not recommend using CBD and/or THC products during pregnancy. There are a number of herbs that are safe for women during pregnancy and can help to combat pain, morning sickness, nausea, and headaches.
National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Board on Population Health and Public Health Practice; Committee on the Health Effects of Marijuana: An Evidence Review and Research Agenda. The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research. Washington (DC): National Academies Press (US); 2017 Jan 12. 10, Prenatal, Perinatal, and Neonatal Exposure to Cannabis. Available from: https://www.ncbi.nlm.nih.gov/books/NBK425751/
Marijuana and Public Health. (2018, March 16). Retrieved from http://www.cdc.gov/marijuana/factsheets/pregnancy.
Eternal Plants. (2018, May 22). A Beginner’s Guide To The Endocannabinoid System. Retrieved from https://eternalplants.com.au/cannabinoids/beginners-guide-endocannabinoid-system/
Dalterio, S., Steger, R., Mayfield, D., & Bartke, A. (1984). Early cannabinoid exposure influences neuroendocrine and reproductive functions in male mice: I. Prenatal exposure. Pharmacology Biochemistry and Behavior,20(1), 107-113.
Purves D, Augustine GJ, Fitzpatrick D, et al., editors. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates; 2001. The Biogenic Amines.
Cristino L, Di Marzo V. Fetal cannabinoid receptors and the “dis-joint-ed” brain. The EMBO Journal. 2014;33(7):665-667. doi:10.1002/embj.201488086.
Calvigioni, D., Hurd, Y., & Harkany, T. (2014). Miswiring the brain: Delta-9-tetrahydrocannabinol disrupts cortical connectivity by inducing SCG10 degradation. European Neuropsychopharmacology,24.
Feinshtein, V., Erez, O., Ben-Zvi, Z., Eshkoli, T., Sheizaf, B., Sheiner, E., & Holcberg, G. (2013). Cannabidiol enhances xenobiotic permeability through the human placental barrier by direct inhibition of breast cancer resistance protein: An ex vivo study. American Journal of Obstetrics and Gynecology,209(6).
Mead, A. (2017). The legal status of cannabis (marijuana) and cannabidiol (CBD) under U.S. law. Epilepsy & Behavior,70, 288-291.
Commissioner, O. O. (n.d.). Public Health Focus – Warning Letters and Test Results for Cannabidiol-Related Products. Retrieved from https://www.fda.gov/newsevents/publichealthfocus/ucm484109.htm