Cannabis Use Linked to Fertility Risks in Women
Cannabis boosts egg maturation but increases chromosome errors, reducing viable embryos in fertility treatment.
Cannabis is one of the most widely used drugs among people of reproductive age, yet its effects on female fertility are only just beginning to be understood.
Researchers at the CReATe Fertility Centre in Toronto, Canada, found that while THC (tetrahydrocannabinol) exposure was linked to higher egg maturation, it also increased errors in chromosomes, leading to fewer healthy embryos.
The study was published in Nature Communications.
Rising cannabis use raises questions about fertility
Cannabis use is increasing worldwide. Legal changes and easier access have led to an increase in the number of people using it – and at higher strengths. In many countries, cannabis is now one of the most common recreational drugs among people of reproductive age. THC, the psychoactive ingredient, has risen in potency from ~3% in the 1980s to ~15% today, with some strains closer to 30%.
THC interacts with the endocannabinoid system, which plays a role in both brain function and reproduction. Research on male fertility shows cannabis can affect sperm count, motility and DNA. There is also evidence linking cannabis use in pregnancy to effects on the placenta and fetal development.
However, the female side of fertility has been harder to study. Very little is known about how cannabis affects oocytes, the eggs that begin embryo development. Access to these cells is limited and most existing studies have focused instead on animal models, with mixed results.
Oocytes are finite in number and sensitive to environmental factors. Any changes in their development could affect fertility and the health of future embryos.
“In humans, we previously demonstrated that THC and its metabolites reach the ovarian follicle,” said the authors of the recent study.
The new research examined how THC exposure influenced human oocytes.
Cannabis exposure affects egg maturation and embryo quality
The team looked at 1,059 follicular fluid samples from in vitro fertilisation (IVF) patients. Around 6% (62) of the samples tested positive for THC metabolites, although 73% of those with THC in their samples had not reported cannabis use.
Concentrations of these metabolites were linked to a higher rate of oocyte maturation; however, the embryos that developed from these oocytes were less likely to have the correct number of chromosomes. Patients who tested positive for THC had a significantly lower rate of euploid embryos compared to matched controls.
Euploid embryos
Embryos that have the correct number of chromosomes, which increases the chance of healthy development and a successful pregnancy.
The second part of the study tested immature oocytes donated by 24 patients in controlled lab experiments. These eggs were exposed to THC levels similar to those found in IVF patients or to higher concentrations reported in animal studies.
At both doses, THC changed gene activity in the oocytes. Many of the affected genes were involved in inflammation, the extracellular matrix and chromosome segregation – processes essential for egg quality and embryo development.
When the researchers looked more closely at these oocytes, they saw more errors in how chromosomes separated, along with abnormal spindle structures. These changes translated into a higher rate of aneuploidy (embryos with the incorrect number of chromosomes).
Spindle structures
The cellular machinery made of microtubules that helps separate chromosomes during cell division. Abnormal spindles can lead to errors in chromosome number.
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The increase in maturation was only observed when THC levels were higher than the average concentrations measured in the IVF patient group.
Fertility counselling should address cannabis risks
THC exposure seemed to push oocytes to mature; however, that came at the cost of genetic stability. For patients undergoing IVF, THC exposure could mean fewer embryos with the right number of chromosomes, which might reduce the number of viable embryos available and lengthen the time to pregnancy.
“These findings underscore the need for increased awareness and caution among people with ovaries, particularly those undergoing fertility treatments,” said the authors.
There are, however, important limits to this work. The oocytes studied were a specific type collected during IVF and may not reflect eggs maturing naturally. The retrospective design also meant there was no information on how often, how much or how cannabis was used. Age is another important factor in oocyte quality, and the study was not powered to separate results by patient age.
Future work will focus on how THC disrupts egg biology at the molecular level, and on larger studies that track pregnancy and live birth outcomes.
“Our study highlights the importance of informing patients about the potential risks associated with cannabis consumption and provides a basis for regulatory bodies, medical professional societies and public health organizations to establish recommendations and guidelines regarding cannabis consumption during fertility treatment,” the authors concluded.
Reference: Duval C, Wyse BA, Weizman NF, Kuznyetsova I, Madjunkova S, Librach CL. Cannabis impacts female fertility as evidenced by an in vitro investigation and a case-control study. Nat Comm. 2025. doi: 10.1038/s41467-025-63011-2
This article is a rework of a press release issued by Springer Nature. Material has been edited for length and content.
