As cannabis legalization sweeps across the globe and recreational use surges, scientists have turned a keen eye to its effects on human fertility—especially for women. Two landmark studies published on September 9, 2025, in Nature Communications have now shed new light on the complex relationship between cannabis consumption and female reproductive health, offering the most comprehensive look yet at how tetrahydrocannabinol (THC), the psychoactive compound in cannabis, may impact the very foundations of conception and early pregnancy.
Until recently, much of the research on cannabis and reproduction focused on male fertility, with established links between THC and altered sperm parameters. But the female side of the equation remained murky—largely due to the technical and ethical challenges of studying human oocytes, or eggs. That’s all changing. According to Nature Communications, researchers led by Duval, Wyse, Fuchs Weizman, and colleagues have now combined cutting-edge laboratory experiments with real-world clinical data from women undergoing fertility treatments, uncovering a web of effects that range from the molecular to the practical.
So, what did they find? The studies took a two-pronged approach. First, they exposed human ovarian and endometrial cells to controlled doses of THC in the lab. This allowed them to observe how cannabinoids interact with the endocannabinoid system—a network of receptors present not just in the brain, but also in reproductive tissues. The results were striking: cannabinoids impaired the viability and hormone function of cells critical for conception, altered the expression of genes involved in oocyte (egg) maturation, and disrupted pathways essential for both follicle development and embryo implantation.
But laboratory results only tell part of the story. To see if these cellular changes translated into real-world fertility challenges, the researchers conducted a case-control study involving over 800 women seeking fertility treatment. Here, they measured THC and its metabolites in follicular fluid—the liquid surrounding eggs in the ovary—and compared clinical outcomes between cannabis users and non-users. The findings were sobering. Women who tested positive for THC had a significantly lower rate of chromosomally normal (euploid) embryos, a key predictor of successful pregnancy, compared to their matched counterparts. In fact, the odds of achieving a euploid embryo rate above 60% dropped by more than half in THC-positive patients.
One of the more nuanced revelations was the dose-dependent nature of these effects. Daily or near-daily cannabis users experienced greater declines in anti-Müllerian hormone (AMH) levels—a biomarker for ovarian reserve—than occasional users or abstainers. This gradation suggests that not only is cannabis use a risk factor for female fertility, but that the risk increases with frequency and quantity of use. According to the study, “cannabis users had markedly reduced ovarian reserve markers and longer times to conception compared to non-users, with a dose-dependent relationship between frequency of use and severity of fertility impairment.”
The research didn’t stop at the ovary. Cannabinoid exposure also disrupted the hypothalamic-pituitary-ovarian axis, the hormonal signaling network that governs ovulation. Specifically, THC exposure was linked to dysregulation of gonadotropin-releasing hormone (GnRH) and suppression of luteinizing hormone (LH) pulsatility, which could explain observed delays in ovulation and lower fertility rates. On the uterine side, cannabinoids impaired the ability of endometrial stromal cells to undergo decidualization—a transformation essential for successful embryo implantation. Failure in this process is a known cause of early pregnancy loss, raising concerns that cannabis’s effects may extend beyond conception to the earliest stages of gestation.
Digging even deeper, the studies used advanced genetic sequencing to examine how THC exposure alters the oocyte transcriptome—the full set of mRNA transcripts stored within the egg. They identified hundreds of genes whose expression was up- or down-regulated by THC, many of them involved in cell signaling, inflammation, cytoskeletal function, and chromosome segregation. Of particular note, genes critical for the cytoskeleton and chromosome alignment were disrupted, and in vitro experiments showed a significant increase in abnormal spindle morphology and chromosome segregation errors in THC-exposed oocytes. This translated to a 9% increase in aneuploidy (abnormal chromosome number) and a higher proportion of complex aneuploidies, both of which are major causes of implantation failure and miscarriage.
“THC exposure led to a 9% increase in aneuploidy rates,” the researchers reported, “and an increase in the proportion of oocytes with complex aneuploidies.” They also found that THC exposure was associated with a significant decrease in embryo euploidy rates in IVF cycles, meaning fewer embryos with the correct number of chromosomes were available for transfer—a crucial factor for couples undergoing fertility treatment.
Surprisingly, while THC exposure was linked to accelerated oocyte nuclear maturation in both clinical and laboratory settings, this apparent boost did not translate into improved fertility outcomes. In fact, the researchers hypothesize that premature or dysregulated maturation could actually increase the risk of chromosomal errors, undermining the chances of a healthy pregnancy. The study suggests that THC may act by binding to cannabinoid receptors on the oocyte surface, inhibiting adenylate cyclase activity, and lowering cAMP levels in the egg—a biochemical cascade that could trigger premature meiotic resumption and chromosome missegregation.
Beyond the immediate effects on fertility, the studies also raised red flags about potential intergenerational consequences. Disrupted ovarian environments and abnormal implantation conditions could, in theory, lead to epigenetic changes in developing embryos, with unknown impacts on offspring health. While this remains an area for future research, the warning is clear: the effects of cannabis may not be limited to the user alone.
Given the rising prevalence of cannabis use—especially among women of reproductive age—and the perception of cannabis as a relatively harmless substance, these findings carry significant public health implications. The researchers recommend that clinicians routinely screen for cannabis use in fertility and reproductive health settings, counsel patients on the potential risks, and consider integrating cessation support into fertility care. They also advocate for public health policies that require reproductive health warnings on cannabis products, much like those mandated for tobacco and alcohol.
Of course, the studies are not without limitations. The retrospective nature of the clinical data means that not all confounding factors—such as other lifestyle habits or co-exposures—could be fully accounted for. And while the laboratory findings are compelling, larger and more diverse longitudinal studies will be needed to establish causality and explore the potential reversibility of cannabis-induced reproductive impairments.
Nevertheless, the message is hard to ignore. As society renegotiates its relationship with cannabis in an era of legalization and changing norms, these studies serve as a timely reminder that the drug’s impact on female fertility is anything but benign. For women hoping to conceive—now or in the future—awareness, education, and open conversations with healthcare providers are more important than ever. The science is catching up, and it’s telling a story that’s far more complicated than many might expect.
