What Are the Effects of Cannabis Use During Pregnancy?

Nancy Hope Goodbar, PharmD


September 12, 2014


How does marijuana affect the pregnant woman and her child?

Response from Nancy Hope Goodbar, PharmD
Assistant Professor of Pharmacy Practice, Presbyterian College School of Pharmacy, Clinton, South Carolina

With the legalization of cannabis in certain states, as well as federal law supporting the utilization of cannabis for medical purposes, there is no doubt that its use is on the rise.[1] The safety of cannabis, either recreationally or medicinally, is a concern for the general population but especially for those who are pregnant or lactating because of the drug's effect on the developing central nervous system (CNS).[2] Although probably grossly underestimated, about 2.5% of pregnant women admit to using cannabis in the United States.[2] Therefore, an understanding of the effects that cannabis has on pregnancy is important for healthcare practitioners.

Cannabis compounds have a small molecular size and are lipophilic in nature which allows for the drug to readily cross the placental barrier.[2] The CB1 receptor, which is the cannabinoid receptor primarily in the CNS, is expressed early in the fetal brain development process and is considered to be critical in neurologic development.[2] Thus, exposure to cannabis during pregnancy could cause hyperstimulation of the CB1 receptor and ultimately affect neuronal signaling and neurophysiologic function, leading to amplified startle reflexes, increased hand-mouth behavior, high-pitched cries, and sleep cycle disturbances.[2,3,4]

Of note, CB1 receptors are also present in placental membranes, and stimulation of these receptors during pregnancy can result in fetal growth restriction.[2,5] Early expression of dopaminergic neurons in the developing fetal brain can lead to disruption of target cell maturation and dopamine function in the presence of cannabis, which puts the fetus at risk for neuropsychiatric disorders.[2]

There is currently no strong evidence linking an increased rate of miscarriages or congenital abnormalities to in utero cannabis exposure.[2,6,7] Significant withdrawal symptoms appear to be uncommon in the newborn exposed to cannabis in utero, but some infants have shown mild withdrawal symptoms similar in presentation to opioid withdrawal.[8] There is currently no pharmacologic therapy that has been studied for cannabis exposure in utero or withdrawal in the neonate.

Population-based human studies and in vitro animal studies evaluating long-term growth and neurodevelopment after exposure to cannabis in utero have shown an effect on both cognition and behavior.[2] In children about 6 years old, lower verbal reasoning scores were associated with heavy cannabis use during the first trimester, and impairment of short-term memory and lower composite and quantitative scores on intelligence testing were associated with heavy cannabis use during the second trimester.[2,9] Evaluation of children born to women who used cannabis throughout pregnancy found significantly higher depressive symptoms and attention problems at 10 years of age and delinquency at 14 years of age compared with those who were not exposed.[2,10,11]

Of course, abstinence from drug use during pregnancy is the optimal situation. Healthcare practitioners should be aware, however, that this may not always be the reality for some patients. Despite the absence of clinical trial data support for this indication, some women use "medicinal cannabis" for management of pregnancy-induced nausea and vomiting.[12]

Although there is literature evaluating the short- and long-term effects of cannabis use during pregnancy, there is still much to be learned regarding its safety. Clinicians should be prepared to discuss the risks with their patients.


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