Help & Guidance — Purple Haze MK
Does THC Affect Fertility?
Yes, THC affects fertility in both men and women. In men it reduces sperm count, motility and DNA integrity. In women, groundbreaking 2025 research published in Nature Communications found THC disrupts chromosome segregation in eggs, reducing healthy embryo rates.
Yes. THC affects fertility in both sexes through multiple mechanisms. In men, studies consistently show that frequent cannabis use reduces sperm count, sperm motility and sperm quality, and causes abnormal sperm morphology. One large study found men who used cannabis more than once a week had a 29% lower total sperm count than non-users. In women, a landmark September 2025 study published in Nature Communications and led by researchers at the University of Toronto was the first to examine THC's effect on human eggs at scale, analysing over 1,000 samples. It found that women with detectable THC in their follicular fluid produced fewer chromosomally normal embryos, raising concerns about miscarriage risk and IVF outcomes. Most experts recommend stopping cannabis use when trying to conceive.
Effects on Male and Female Fertility
THC and male fertility
- Men using cannabis more than once a week show a 28 to 29% reduction in sperm concentration and total sperm count compared to non-users
- Increased percentage of abnormally shaped sperm (poor morphology), reducing fertilisation capacity
- Impaired sperm motility, meaning sperm are less able to reach and penetrate an egg
- Reduced testosterone levels with frequent use, which is essential for sperm production
- Altered DNA methylation in sperm, with potential implications for offspring development
- THC triggers premature sperm capacitation, causing sperm to expend their fertilisation energy too early
- Many of these effects appear reversible with cessation of cannabis use, according to primate studies
THC and female fertility
- THC and its metabolites reach the ovarian follicular fluid, directly exposing developing eggs to the compound
- The 2025 Nature Communications study found THC-positive patients had significantly lower euploid (chromosomally normal) embryo rates than matched controls
- THC disrupts chromosome segregation during the final stages of egg maturation, the process that prepares an egg for fertilisation
- Chromosomal abnormalities in embryos are a major cause of miscarriage and failed IVF cycles
- THC may alter the expression of genes involved in chromosome segregation, inflammation and extracellular matrix remodelling in eggs
- Notably, 73% of women who tested positive for follicular fluid THC had not disclosed cannabis use to their treating clinicians
Reduction in total sperm count in men using cannabis more than once a week compared to non-users
Women with THC in follicular fluid had significantly lower rates of chromosomally normal embryos in the 2025 Nature Communications study
Male fertility effects from THC appear largely reversible after stopping cannabis use, based on current evidence
The 2025 Nature Communications Study on Female Fertility
Prior to September 2025 there was a significant gap in research: while THC's effects on sperm were well studied, almost no human data existed on its effects on eggs and female fertility. Researcher Cyntia Duval at the University of Toronto addressed this directly. Analysing ovarian follicular fluid from more than 1,000 patients undergoing IVF treatment, and comparing 62 women who tested positive for THC against matched controls, the study found two key findings.
First, women with detectable THC in their follicular fluid had a higher egg maturation rate. This initially sounds positive but is misleading. The second finding explains why: these same women produced fewer embryos with the correct number of chromosomes. The eggs were maturing faster than they should, disrupting the precise timing required for chromosomes to align correctly before fertilisation. Incorrect chromosome numbers in embryos (aneuploidy) are the leading cause of miscarriage and a major reason for failed IVF cycles. The researchers also observed that THC induced chromosome segregation errors and abnormal spindle morphology in eggs directly, in laboratory conditions.
The study was described by independent fertility specialists as an exciting and novel contribution filling a critical gap in knowledge. Dr Jamie Lo, an obstetrician at Oregon Health and Science University, said the findings support a harm-reduction approach and highlight the importance of caution when using cannabis while planning to conceive.
How THC Reaches Reproductive Tissue
THC is highly lipophilic, meaning it dissolves readily in fat and is absorbed into fatty tissues throughout the body. It is distributed widely via the bloodstream and can cross biological membranes that many other compounds cannot. In women, THC and its metabolites have been detected directly in follicular fluid, the liquid surrounding developing eggs in the ovaries. In men, THC reaches the testes and has been found to affect the spermatogenic process at multiple stages. The endocannabinoid system, which THC acts on, is naturally present in reproductive tissue in both sexes, meaning the machinery for THC to affect fertility is biologically in place.
For more on cannabis and health, visit the Purple Haze MK Help and Guidance Centre.
Cannabis is a Class B controlled drug in the UK and is illegal to possess or supply. This page is informational for those researching the topic. If you are trying to conceive and have questions about cannabis use, speak to your GP or a fertility specialist. Both the male and female partner's cannabis use is relevant to conception outcomes, not just one partner.
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Frequently Asked Questions
Does cannabis affect fertility in both men and women?
Yes. Evidence exists for fertility effects in both sexes. In men, multiple studies consistently show reductions in sperm count, motility and quality with regular use. In women, the 2025 Nature Communications study provided the first large-scale human evidence that THC disrupts chromosome segregation in eggs and reduces the proportion of chromosomally normal embryos. The picture is clearer for male fertility due to the longer history of research, but female fertility is now catching up.
Does stopping cannabis use restore fertility?
For men, the evidence from primate studies suggests that the reduction in testosterone and sperm quality associated with THC exposure can be reversed after stopping use. New sperm takes approximately 74 days to develop (a full spermatogenesis cycle), so a minimum of two to three months of abstinence before trying to conceive gives new sperm time to form without THC exposure. For women, the effects on egg maturation and chromosome segregation are less studied in terms of reversibility, but stopping cannabis use well before attempting conception is the recommended precautionary approach.
Does cannabis use affect IVF success rates?
The 2025 Nature Communications research found that women with detectable follicular fluid THC had significantly lower rates of chromosomally normal embryos, which is a key predictor of IVF success. Fewer healthy embryos means fewer viable embryos to transfer, lower implantation rates and higher miscarriage risk. If you are undergoing or planning IVF, stopping cannabis use well in advance is strongly advisable based on this evidence.
Is CBD safer than THC for fertility?
CBD is not known to cause the same reproductive harm as THC. The endocannabinoid system does play a role in reproduction, and some research suggests CBD is not entirely risk-free during pregnancy. However, the volume of evidence on CBD's fertility effects is far smaller than for THC, and CBD does not carry the same chromosomal disruption mechanism identified for THC. If fertility is a concern, discuss CBD use with your GP or fertility specialist before continuing.
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