A review found that the endocannabinoid system is involved in normal placenta development, and THC exposure can disrupt trophoblast cell proliferation, death, and function, potentially explaining cannabis-related fetal growth restriction.
Pregnant individuals and clinicians interested in the biological basis of cannabis effects on pregnancy.
THC disrupts the endocannabinoid signaling that normally guides placental development
What the researchers found
This review examined how the endocannabinoid system participates in normal human placenta development and how cannabis use may disrupt this process.
The endocannabinoid system is expressed in human placentas and plays roles in trophoblast cell proliferation, apoptosis (programmed cell death), differentiation, and function. Abnormal expression of this system has been associated with infertility and miscarriages.
THC, which activates the same cannabinoid receptors as endogenous endocannabinoids, can interfere with these tightly regulated processes. The review argued that this provides a biological mechanism for the clinical observation that cannabis use during pregnancy is associated with fetal growth restriction.
Why it matters
Understanding the biological mechanisms by which cannabis affects pregnancy outcomes is important for both clinical advice and research priorities. This review moves beyond epidemiological associations to provide mechanistic explanations for fetal growth restriction.
The numbers in context
No specific quantitative data presented. The review synthesized findings on cannabinoid receptor expression in placental tissue and the effects of eCBs and THC on trophoblast cell behavior.
How the study worked
Review article examining published literature on endocannabinoid system expression and function in normal and pathological human placentas, and the effects of THC and endocannabinoids on trophoblast biology.
What this study cannot tell us
Much of the evidence comes from in vitro studies of placental cells rather than whole-organism research. The concentrations of cannabinoids used in cell studies may not reflect actual placental exposure during cannabis use. Individual variability in placental cannabinoid receptor expression is not well characterized.
How to read the evidence
This is a mechanistic review drawing on cell biology and placental tissue studies, providing moderate evidence for a biological pathway linking cannabis to fetal growth restriction.
When this study was published
Published in 2016. Research on cannabis and placental biology has continued to advance.
The bigger picture
The endocannabinoid system turns out to be important in many reproductive processes, from implantation to placental development to fetal growth. This creates multiple points at which cannabis use could interfere with normal pregnancy progression.
Questions still open
- At what gestational stage is the placenta most vulnerable to cannabinoid disruption? Could CBD-only products affect placental development through the same mechanisms?
Common questions
How does cannabis affect the placenta?
Is any amount of cannabis safe during pregnancy?
Read the original research
The endocannabinoid system: A novel player in human placentation.
Reproductive toxicology (Elmsford, N.Y.), 61, 58-67
Citation
Costa, M A. (2016). The endocannabinoid system: A novel player in human placentation.. Reproductive toxicology (Elmsford, N.Y.), 61, 58-67. https://doi.org/10.1016/j.reprotox.2016.03.002
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