Rationale: As more people of child-bearing age are using cannabis, research on its health impacts has also risen. THC is known to decrease sperm concentration and motility, and this study focused on its effects on oocytes. THC readily penetrates ovaries and may disrupt the follicular environment to impact ovarian cells. 

Method: Researchers collected immature oocytes and follicular fluid from female volunteers. Oocyte samples with no traces of THC were cultured with either: no, low, or high concentration of THC. Researchers evaluated a range of effects including cannabis’ influence on gene expression and chromosomal changes.

Results: Oocytes exposed to THC had more chromosomal errors; the structures within the chromosomes were 50% more likely to be abnormal than unexposed cells. Embryos derived from oocytes exposed to THC also had a higher amount of chromosomes with deformities.

Although researchers did not include oocyte samples positive for THC before experiment, 6% of follicular fluid contained THC metabolites, suggesting sustained effects. THC dose-dependently affected gene activity in oocytes. While low dose THC mostly suppressed gene activity, high dose THC turned on cell death pathways, suppressed genes that regulate immune and inflammatory responses, and interfered with cell division.

Meaning: THC alters genes in the female egg cells of developing babies, which can affect their future offspring. THC exposure led to more deformities in embryos and altered the expression of hundreds of genes. Cannabis use in women may have long-lasting impacts on future generations.