Occasional marijuana use during pregnancy involves the infrequent consumption of cannabis products by an expectant mother, through methods like smoking, vaping, or ingesting edibles. This article provides information on how these substances interact with the developing fetus and the pregnant individual, drawing from current scientific understanding.
How Cannabis Compounds Reach the Fetus
When a pregnant individual uses marijuana, active compounds like delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) are absorbed into the mother’s bloodstream. Both THC, the main psychoactive component, and CBD readily cross the placental barrier.
The placenta, while serving as a protective interface, is not an absolute barrier against all substances. Both THC and CBD are highly fat-soluble, which allows them to easily cross cell membranes, including those of the placenta. Once these cannabinoids cross into the fetal circulation, they can enter the fetal brain. Cannabinoid receptors have been identified in the fetal brain and placenta as early as 14 weeks of gestation, suggesting a system that can interact with these compounds.
Studies in animal models show that THC concentrations in fetal blood can be a fraction of maternal concentrations, though this varies by delivery method. Research also indicates that cannabis can affect the placenta’s normal transport mechanisms and physiology, potentially enhancing the placental barrier’s permeability to other substances.
Potential Effects on Fetal Development
Prenatal cannabis exposure can have several consequences for the developing fetus and child. One recognized outcome is a reduction in birth weight and head circumference. Studies indicate that even occasional use during the first trimester can significantly reduce birth weight, with continued use leading to more pronounced changes. Offspring exposed to THC, CBD, or a combination of both during gestation have been born with lower body weights, indicating fetal growth restriction.
Beyond immediate birth outcomes, prenatal cannabis exposure is associated with neurodevelopmental effects. Cannabinoid receptors are present in the fetal brain, and the endocannabinoid system plays a role in brain circuit formation. Disruptions to this system by exogenous cannabinoids can lead to alterations in neurotransmitters, particularly in dopamine pathways. Long-term studies have revealed an increased risk for cognitive impairment, attention problems, and behavioral difficulties in children exposed to cannabis in the womb.
Specific neurobehavioral conditions, such as autism spectrum disorder and attention deficit hyperactivity disorder, have been linked to changes in gene regulation and expression observed in non-human primate models exposed to THC. Children of mothers who used larger amounts of cannabis in the first trimester have shown higher rates of anxiety and depression, as well as behavioral problems by approximately two years of age. By ten years old, these children may experience increased rates of depression and difficulties with learning and concentration. Some research also suggests a slightly higher risk of stillbirth and an increased risk of anencephaly, a severe neural tube defect, with prenatal marijuana exposure.
Maternal Health Considerations
Occasional marijuana use during pregnancy can impact the pregnant person’s health in various ways. Despite anecdotal beliefs that it may alleviate morning sickness, there is no scientific evidence supporting this, and health organizations advise against its use for this purpose. A large study indicated a link between cannabis use in early pregnancy and an increased risk of gestational hypertension, a form of high blood pressure. This risk appeared to increase with more frequent reported cannabis use.
Preeclampsia, a serious pregnancy complication characterized by high blood pressure, also shows an increased risk among pregnant individuals who use cannabis. Studies have associated maternal cannabis use with an increased risk of placental abruption, a condition where the placenta detaches from the uterus prematurely. This can pose serious risks to both the mother and the baby. Cannabis use during pregnancy has also been linked to both excessive and insufficient gestational weight gain, which can lead to further health complications.
Professional Health Recommendations
Major health organizations consistently advise against any cannabis use during pregnancy. The American College of Obstetricians and Gynecologists (ACOG) recommends that clinicians discourage the use of marijuana during preconception, pregnancy, and lactation periods. This guidance stems from concerns regarding impaired neurodevelopment in the offspring, as well as the general lack of safety data.
ACOG suggests that if a pregnant person is considering cannabis for medicinal purposes, they should pursue alternative therapies with better pregnancy-specific safety data. The Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) also align with these recommendations, emphasizing that no amount of marijuana has been proven safe to use during pregnancy. The rationale behind these guidelines is rooted in the precautionary principle, given the potential for harm and the insufficient understanding of all possible effects on both maternal and fetal health. Health professionals are encouraged to discuss these consequences with patients and offer support for discontinuing use.