A combined clinical and laboratory study found that THC reaches the ovarian follicle, where higher concentrations correlated with oocyte maturation but THC-positive fertility patients had significantly lower rates of chromosomally normal embryos, and lab experiments showed THC caused chromosome segregation errors.
Women trying to conceive, fertility patients, and reproductive health clinicians.
THC-positive fertility patients had significantly lower embryo euploidy rates than matched controls
What the researchers found
In the clinical study, follicular fluid THC concentration was positively correlated with oocyte maturation, but THC-positive patients had significantly lower embryo euploid (chromosomally normal) rates than matched controls. In the lab, THC induced oocyte chromosome segregation errors, increased abnormal spindle morphology, and altered expression of genes involved in extracellular matrix remodeling, inflammation, and chromosome segregation.
Why it matters
This is the first study to directly examine THC's effects on human oocytes (eggs). The finding that THC causes chromosome segregation errors provides a biological mechanism for reduced fertility and potentially increased risk of chromosomally abnormal pregnancies in cannabis users.
The numbers in context
THC-positive patients had significantly lower embryo euploid rates than matched controls. In vitro THC exposure increased chromosome segregation errors and abnormal spindle morphology. Gene expression changes in extracellular matrix remodeling, inflammation, and chromosome segregation pathways.
How the study worked
Two-pronged approach: (1) Case-control study comparing fertility patients who tested positive for THC in follicular fluid with matched controls, examining oocyte maturation and embryo euploidy rates. (2) In vitro experiments exposing human oocytes to THC and measuring chromosome segregation, spindle morphology, and gene expression. Published in Nature Communications.
What this study cannot tell us
The clinical component is a case-control study, not a randomized trial. THC exposure in the lab may not replicate the complexity of in vivo exposure. The sample size for the clinical study was not detailed in the abstract. Follicular fluid THC levels may not reflect chronic exposure patterns.
How to read the evidence
Published in Nature Communications with both clinical case-control data and in vitro mechanistic evidence, providing strong convergent evidence for a specific biological pathway.
When this study was published
Published in 2025.
The bigger picture
While extensive research has examined THC's effects on sperm, this is the first comparable investigation for oocytes. The paradox of increased oocyte maturation but decreased embryo quality suggests THC may accelerate maturation in a way that compromises subsequent development, a pattern seen with other reproductive toxicants. Published in Nature Communications, this carries significant scientific weight.
Questions still open
- How long before conception should cannabis use stop to avoid oocyte effects? Does the chromosome segregation risk translate to higher miscarriage rates or birth defects? Is there a dose threshold below which THC does not affect oocyte quality?
Common questions
Can cannabis affect egg quality?
Should I stop cannabis if trying to conceive?
Read the original research
Cannabis impacts female fertility as evidenced by an in vitro investigation and a case-control study.
Nature communications, 16(1), 8185
Citation
Duval, Cyntia; Wyse, Brandon A; Fuchs Weizman, Noga; Kuznyetsova, Iryna; Madjunkova, Svetlana; Librach, Clifford L. (2025). Cannabis impacts female fertility as evidenced by an in vitro investigation and a case-control study.. Nature communications, 16(1), 8185. https://doi.org/10.1038/s41467-025-63011-2
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