Cannabis May Disrupt Female Fertility, Fuel Chromosome Errors
September 23, 2025
Cannabis consumption may adversely affect female fertility by impairing egg quality and other factors involved in embryo development, new research suggested.
In a study that included both clinical and in vitro analyses of cannabis use and the impact of tetrahydrocannabinol (THC) on female fertility, the authors found that “THC exposure seems to impact critical [gene] transcripts involved in key oocyte maturation processes, fertilization, early embryo development, and implantation.”
Simply put, higher THC concentrations were associated with higher rates of egg maturation but lower rates of embryos with the correct number of chromosomes, according to lead author Cyntia Duval, PhD, director of Translational Research at CReATe Fertility Centre, an in vitro fertilization (IVF) clinic affiliated with the University of Toronto, Toronto, and colleagues.
“So, THC is ‘pushing’ the maturation, bypassing the safety mechanism that usually allows the chromosomes to segregate correctly,” Duval told Medscape Medical News. “If you’re trying to conceive, and especially if you are an IVF patient, if you consume cannabis, you might reduce the number of embryos that will be transferable.”
The findings were published online on September 9 in Nature Communications.
‘A Word of Caution’
Researchers conducted two studies to assess the potential impact of THC on fertility.
For their in vitro study, the team collected immature oocytes that were not going to be used for IVF treatment from patients who tested negative for cannabinoids. They matured the immature oocytes in vitro for 24 hours with and without THC and its metabolites.
THC exposure during maturation increased the proportion of aneuploidy, or oocytes with an incorrect number of chromosomes. Moreover, it altered the spindles, the cellular machinery that correctly separates chromosomes.
In their retrospective case-control study, the researchers used mass spectrometry to quantify the concentration of THC and its metabolites in the follicular fluid of 1059 women who had IVF treatment from 2016 to 2023. About 62 women had THC in their follicular fluid.
Women with higher THC levels in their follicular fluid had more mature oocytes than women with no THC. However, THC was associated with altered chromosome segregation, the process during cell division in which a cell ensures that each new daughter cell in the embryo receives a complete and accurate set of chromosomes.
“Higher concentrations of THC were associated with more mature oocytes, ready to be fertilized,” Duval said. “So, there were more mature oocytes, but also fewer embryos with the right number of chromosomes.”
Patients who are trying to conceive should be aware that cannabis use might make an impact, she noted. “I’m not putting this out there to make laws banning cannabis. It’s just a word of caution.”
Furthermore, she added, “We don’t know if there’s a washout period in females.” Spermatogenesis is an ongoing process in men. Therefore, clinicians generally will suggest stopping or reducing cannabis consumption for 3 months prior to trying to conceive.
But because it’s assumed that women have a finite number of eggs, determined at birth, it’s not known whether cannabis use has long-term effects or if stopping its use will have an impact. That’s something that must be tested in animal models, Duval suggested.
‘Mechanism Clarified’
“This is an important study, as it clarifies the mechanism by which THC is harmful to female fertility,” Beth Taylor, MD, reproductive endocrinologist and IVF specialist at Olive Fertility Centre, Vancouver, commented to Medscape Medical News.
Among the strengths of the study was the combining of the in vitro and clinical studies, she noted.
“It helps us to explain to our patients why avoiding THC is important by actually revealing the mechanism,” she said. “When patients understand there is a known mechanism of harm from an exposure, they are more likely to avoid the exposure. This information is important to give to our patients so they can make informed decisions about their reproductive health.”
The study was funded by CReATe Fertility Centre through the reinvestment of clinical earnings. Duval and Taylor reported having no relevant financial relationships.
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