Women who are pregnant should avoid using marijuana.
“We have to get behind the message that marijuana is on the same level as smoking or alcohol use during pregnancy,” said Nathaniel G. DeNicola, MD, MSc, University of Pennsylvania Social Media & Health Innovation Lab. “We already recommend no safe amount of tobacco during pregnancy, no safe amount of alcohol during pregnancy. We should be recommending no safe level of marijuana during pregnancy.”
ACOG recommends counseling women against the use of marijuana during pregnancy, Dr. DeNicola noted, while the American Academy of Pediatrics terms breast feeding a contraindication to marijuana use. He explored the often-sketchy data behind both positions during a Sunday clinical seminar on the “Highs and Lows of Marijuana in Obstetrics & Gynecology.”
The reality is that marijuana use is increasing dramatically as it moves toward legalization in more places. California legalized the medical use of marijuana in 1995; today, medical use is legal in 23 states and due to become legal soon in Pennsylvania. Recreational use is legal in only three states, but both recreational use and self-medication are common nationwide.
“In recent years, alcohol use remains unchanged, and tobacco use is down,” Dr. DeNicola said. “Marijuana use is up 130 percent. Peak use for marijuana is in the 20s and 30s, women’s peak reproductive years.”
Common uses include pain relief, relief of nausea and vomiting from cancer chemotherapy, appetite stimulation in AIDS and cancer, treatment of sleep disorders and neuropathic pain, relief of spasticity in multiple sclerosis and Parkinson’s, seizure disorders, glaucoma, and a variety of anxiety disorders. Marijuana is also used as an antiemetic during pregnancy, although what little data exist suggest that it more likely promotes nausea than calms it.
The major cannabinoids in marijuana include tetrahydrocannabinol (THC), the primary psychoactive ingredient, and cannabidiol (CBD), which has no psychoactive properties. The Food and Drug Administration has approved two cannabinoids, dronabinol (Schedule III) and nabilone (Schedule II). A liquid extract, Nabiximols, is in phase III trials following approval in 24 countries, and cannabidiol has been granted orphan drug status for Dravet and Lennox-Gestaut syndromes. Botanical marijuana remains Schedule I.
THC is a lipophilic chemical that perfuses quickly into blood, brain, liver, placenta, and breast milk and also clears quickly from these tissues. Cannabinoids are metabolized in the liver.
Cannabinoid receptors CB1 and CB2 are found throughout the body. Endocannabinoids play key roles in normal development.
The fetal brain has a higher level of CB1 receptors than the adult brain, possibly because the endocannabinoid system plays key roles in metabolic support, axonal elongation, cell proliferation and migration, synaptogenesis, and neuroprotection for neurotransmitters in the central nervous system. Marijuana use creates the potential for supra-physiological stimulation of the endogenous cannabinoid system and its activities.
Potential harms include disrupted endocannabinoid signaling, disruption in the formation of synapses and neuronal connections , impairment of axon development and growth disruptions.
There is some evidence of decreased fetal growth, decreased IQ scores, decreased cognitive function and attention problems in children exposed to marijuana in utero, Dr. DeNicola said. The few studies that have been completed are limited by concurrent use of other substances, self-reporting bias, recruiting issues and loss of subjects to follow up. There are also a variety of confounding factors, including environment, family history, maternal cognitive ability and socioeconomic status.
“We already know from reductions in use of tobacco and alcohol that pregnancy can be a very powerful motivator,” he said. “We should be giving the same message that marijuana use should be eliminated in pregnancy.”
