Can cannabis affect your chances of getting pregnant? New research provides answers

A recent study published in Nature Communications by Cyntia Duval and colleagues from the University of Toronto suggest that the THC could interfere with fertility of women

Previous work by Duval's team had already demonstrated that THC and its metabolites can cross the ovarian follicle, the microenvironment surrounding the ovum. This new study confirms the consequences of this exposure.

Of the 1,059 ovarian fluid samples analyzed from IVF patients, 6% proved to be positive for THC metabolites. Note that 73% of these patients had not reported cannabis use, This suggests that many women underestimate or under-report their consumption when undergoing fertility treatment.

Faster egg maturation, but at a price

The researchers discovered that higher THC levels were correlated with increased egg maturation rate. At first sight, this may seem beneficial, as mature eggs are necessary for fertilization. But the speed of maturation seemed to have a drawback: the eggs of THC-positive patients showed significantly lower embryonic euploidy rates, This means fewer embryos with the correct number of chromosomes.

In figures: the euploidy rate was 67% in control group vs. 60% in THC-positive group. Logistic regression confirmed that THC exposure was independently related to this reduction. Given that chromosomally normal embryos are essential for implantation and healthy pregnancy, this reduction could result in a higher risk of IVF failure or miscarriage.

In the lab: THC alters chromosomes and spindles

To better understand the mechanism, the team exposed immature eggs to physiologically relevant concentrations of THC in vitro. The results revealed:

• Transcriptomic changes 316 genes were deregulated at realistic THC levels, and over 460 at higher doses. Many were linked to’inflammation, extracellular matrix remodeling and chromosome segregation
• Chromosome segregation errors THC-exposed eggs showed a 9 % increase in aneuploidy, that is, an abnormal number of chromosomes. Complex aneuploidies (loss or gain of three or more chromosomes) were observed in 42 % of THC-exposed eggs, compared with none in controls.
• Abnormal spindle morphology The structures that align chromosomes for division were disrupted in THC-treated eggs. At higher doses, 92 % had abnormal spindles, compared with 42 % in controls

These anomalies are crucial, as errors at this stage can prevent embryo development or lead to complications during pregnancy.

The authors conclude that exposure to THC can prematurely accelerate egg maturation, disrupting the delicate process of chromosome alignment. This can reduce the chances of producing chromosomally normal embryos, leading to longer conception times, failed IVF cycles or miscarriages.

Although the study was limited by the relatively small number of THC-positive patients and the fact that the in vitro tests used immature eggs not intended for clinical use, the results present convincing biological evidence.

Power and hidden exposure risks

The study also highlights a broader concern: modern cannabis products contain much higher THC levels than in the past. In the 1980s, cannabis contained an average of around 3% of THC. Today, many strains exceed 15%, and concentrates can reach 30% or more. This means that women can expose their eggs to higher levels of THC than ever before, even if they use it only occasionally.

As labelling is not always reliable, particularly in unregulated markets, patients may unknowingly underestimate their consumption.

Although further research is needed to confirm these findings in larger populations and in the context of natural conception, the message from this study is clear: THC can reach human eggs and alter their development at the chromosomal level.

«Our results reveal significant effects on oocyte maturation, transcriptomic profiles, meiotic spindle organization and oocyte ploidy,» Duval and colleagues write. «Collectively, these data present compelling evidence that cannabis use can have a negative impact on female fertility.»

For the time being, experts suggest that women undergoing fertility treatment or planning a pregnancy should consider reduce or stop their cannabis use to minimize reproductive risks.