Cannabis may cause unexpected fertility issues in women

Cannabis carries two faces in today’s world. On one side, it’s medicine. On the other, it’s a drug with unknown costs. Many women turn to it for nausea, stress, or pain relief. Yet scientists are raising alarms about what it might be doing to eggs inside the ovary.

A new study shows THC, the compound that makes people feel high, can seep into the follicular fluid where eggs grow.

Once there, it doesn’t just sit quietly. It changes how eggs mature and may set the stage for genetic mistakes. That raises hard questions about fertility, miscarriages, and the health of future children.

THC found in ovaries

The research team collected more than a thousand samples of follicular fluid from women in fertility clinics. About six percent contained THC, even though most of these patients hadn’t reported cannabis use. That means eggs were exposed to cannabis whether the women realized it or not.

Eggs from THC-positive patients matured faster. At first glance, that sounds like a good thing. But the study showed a twist. Those same patients produced fewer embryos with the right number of chromosomes. Faster wasn’t better – it was riskier.

“The findings of this study are concerning and highlight the importance of a cautious approach in using cannabis when planning to conceive,” said Dr. Jamie Lo, an obstetrician at Oregon Health & Science University.

How cannabis may affect fertility

Ovarian follicles are tiny sacs that prepare eggs for fertilization. The timing of this process matters. Rushing it can leave the egg unprepared.

THC appears to trigger early changes by interacting with cannabinoid receptors. This likely lowers levels of cyclic AMP, a molecule that normally prevents eggs from maturing too soon.

When eggs race ahead, chromosomes don’t always line up properly. Under the microscope, THC-exposed eggs showed spindles that were broken, misplaced, or multipolar.

These are the very structures that should guide chromosomes during division. When they fail, the result is aneuploidy – embryos with missing or extra chromosomes.

“This is a hypothesis, and the worst thing I would want is for the public to read this and become fearful. More studies are needed to verify our findings and determine how or even if the changes we observed affect reproduction,” noted study lead author Cyntia Duval.

Shifts in gene activity

The team also examined which genes switched on or off inside eggs exposed to THC. They found hundreds of changes. Many genes tied to inflammation, cell structure, and embryo survival showed altered activity.

One important example is MMP9, a gene critical for breaking down tissue so embryos can implant. THC exposure reduced its expression.

Other signals, like interleukin-33 and interferon-gamma, also dropped. These molecules help prepare the uterus for implantation. Without them, the odds of miscarriage climb.

Eggs rely on precise gene activity to build reserves of RNA and proteins before fertilization. If THC scrambles that preparation, embryos may falter in the first days of life.

Cannabis and fertility treatments

In real fertility treatments, the impact was clear. Women with THC in their ovarian fluid had fewer healthy embryos to transfer.

For those trying naturally, this might mean longer waits to conceive, more miscarriages, or fewer chances of success.

“The finding that exposure to higher levels of THC could be associated with worsened fertility and increased reproductive complications may help patients that cannot abstain from cannabis with a harm-reduction strategy,” Lo said.

The cannabis potency problem

Potency has changed the landscape. Decades ago, marijuana contained about three percent THC. Today, dispensaries sell strains that easily top 30 percent. Extracts and concentrates climb past 40 percent.

“However, certain types of cannabis are typically more potent than others – cannabis extracts are typically more potent than cannabis flower,” said Tom Freeman, a professor of psychology at the University of Bath.

People often try to adjust by smoking less or inhaling lightly. But as Freeman pointed out, these efforts rarely balance the equation. “Higher potency products still deliver a larger dose of THC to consumers than lower potency products,” he said.

Why it matters now

Eggs are not renewable. Women are born with all they will ever have. Damage to these cells carries lasting consequences.

Unlike sperm, which regenerate daily, eggs cannot be replaced. If THC harms them, the effects echo across fertility and pregnancy outcomes.

“Because it’s hard to know the specific level of THC in various cannabis products on the shelves, I advise my patients to consider safer alternatives to treat the symptoms they’re using cannabis for or at least try to reduce the frequency of their use,” said Lo.

Future research on cannabis and fertility

This study doesn’t close the book. It opens it. The findings highlight real risks, but more work is needed to prove direct cause and effect.

Scientists need larger samples, longer follow-ups, and data from natural conceptions, not just fertility clinics.

Still, the warning is clear. THC speeds egg maturation, disturbs chromosomes, and alters gene activity. It may not stop conception entirely, but it may lower the odds of healthy embryos. For women planning pregnancies, this information could make all the difference.

The study is published in the journal Nature.

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