Study shows cannabis use may hurt fertility of females doing IVF

A recent study led by University of Toronto researchers has found that cannabis use may harm the egg health of females undergoing fertility treatments.

The findings reveal a “need for increased awareness and caution among people with ovaries” about cannabis use during in vitro fertilization (IVF), the researchers write in their study.

The research, published in Nature Communications, had two parts: an in vitro investigation and a case control study, each looking at tetrahydrocannabinol (THC) and its effects on the oocyte, which is a cell in the female ovary.

Both parts of the study found that THC may have a negative effect on egg quality.

“THC and its metabolites may be associated with chromosome segregation errors, in both oocytes and embryos,” says Cyntia Duval, lead researcher on the study.

“If an embryo doesn’t have the right number of chromosomes, it would not be considered transferrable, and might result in less embryos available for transfer, if they are classified as aneuploid.”

Duval did the research for the study when she was a postdoctoral fellow at the Temerty Faculty of Medicine’s department of physiology from June 2022 to August 2025, before assuming the role of director of translational research at CReATe Fertility Centre, where she is now based.

Clifford Librach, a professor of physiology and obstetrics and gynaecology at Temerty Medicine and founder and director of CReATe, supervised Duval’s research while she was a postdoctoral fellow. He is also a co-author of the study.

The researchers looked at donated biological samples, including de-identified immature oocytes and follicular fluid, from more than 1,000 females doing IVF at CReATe.

“One part of the research was a retrospective study. We measured the presence of cannabinoids coming from cannabis in follicular fluid samples,” says Duval.

“In this part of the study, we saw a correlation between the concentration of THC and its metabolites, and oocyte maturation, which is when the oocyte is at a certain stage where it’s ready to be fertilized and used for IVF. We also saw a decrease of the proportion of euploid embryos, which means embryos with the right number of chromosomes.”

The second part of the research extended the findings of the first part.

“The second part was an in vitro study on oocytes negative to phytocannabinoids and that were considered to be immature,” says Duval. “I collected them, matured them in vitro, and exposed them to THC and its metabolites and saw the same trend of increased maturation.”

This led her to look at the ploidy status of the oocytes, or number of complete sets of chromosomes, which showed THC altering chromosome segregation, she adds.

Ultimately, the researchers concluded in the study that “exposure to THC affects oocyte maturation, transcriptome, and induces meiotic chromosomal imbalances associated with altered spindle morphology.”

They also write that there is “compelling evidence that cannabis consumption may negatively impact female fertility.” 

The study notes that people who undergo IVF treatment are warned about drug use, and 73 per cent of patients whose follicular fluid was positive for THC did not mention drug use during their intake process.

“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 researchers write.