Cannabis use linked to changes in female fertility

Cannabis is one of the most widely used recreational substances worldwide. Although there are numerous studies on the effect of tetrahydrocannabinol (THC) —the main psychoactive compound in cannabis— on the endocrine system and fertility, most of this research has focused on male fertility. Until now, there has been little information on the impact of cannabis on female gametes.

A team led by Cyntia Duval conducted a retrospective case-control study, analysing 1,059 follicular fluid samples from patients undergoing in vitro fertilisation treatments. The aim was to assess how physiologically relevant concentrations of THC affect oocyte maturation, as well as the transcriptomic changes and chromosomal alterations caused by exposure to THC. The results of these tests were compared with a retrospective cohort study.

Of the total samples, 6% tested positive for THC metabolites, indicating recent cannabis use. This percentage is lower than that observed in the general population, as patients undergoing reproductive treatment are advised to avoid drug use. In fact, 73% of the positive samples were from women who had initially reported not using cannabis.

The researchers observed that higher concentrations of THC metabolites negatively affect egg maturation, alter gene expression, and cause chromosomal problems. These alterations were associated with abnormal mitotic spindle morphology and a lower number of embryos with correct karyotypes compared to the control group.

In additional laboratory experiments, immature oocytes from 24 patients were exposed to THC levels similar to those found in the ovaries of the 62 patients mentioned above. The results showed an increase in the rate of errors in chromosome distribution.

This study represents a significant advance in understanding the effects of cannabis on female fertility, as it is the first to directly analyse the oocyte from the perspective of its maturation and genetic alterations. However, it has certain limitations, such as the use of immature oocytes in the germinal vesicle (GV) stage after ovarian hyperstimulation—which are not ideal for reproduction—and the lack of statistical power to analyse the results according to the age of the patients, as 81% of the GV oocytes came from women under the age of 37.

These findings contribute to a better understanding of the specific reproductive consequences of cannabis use in women and underscore the importance of informing them about the potential risks, especially those undergoing fertility treatments. The study lays the groundwork for regulatory bodies and public health entities to establish clear recommendations on cannabis use during fertility treatments.