Marijuana could disrupt human egg development and cause chromosomal defects

Researchers discovered that exposure to THC, the psychoactive component of cannabis, may interfere with how oocytes (unfertilized eggs) mature, raising concerns about fertility, miscarriage, and even genetic conditions in future offspring.

THC Exposure Tied to Chromosomal Errors

The study showed that higher THC levels were associated with changes in egg development and an increase in chromosomal defects.

This disruption in how eggs mature could prevent them from properly aligning their chromosomes, a crucial step before fertilization. Though the research shows correlation, not causation, scientists say the findings are significant enough to warrant caution.

“Concerning Findings,” Say Experts

“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 and associate professor at Oregon Health & Science University.

Though not involved in the study, Lo called the research “exciting and novel,” as previous work focused mostly on how cannabis affects sperm.

A Rising Trend in Pregnancy Use

Use of marijuana during pregnancy has soared. A 2023 study found that self-reported cannabis use among pregnant women in the U.S. more than tripled between 2002 and 2020.

Despite growing evidence linking cannabis to autism, low birth weight, preterm delivery, and even infant death, many still believe it’s a safe option for managing nausea and discomfort.

Eggs May Mature Too Quickly

In a sample of over 1,000 ovarian fluid samples, researchers compared oocytes from 62 THC-positive women with a matched THC-free control group.

While eggs exposed to THC matured faster, they often lacked the correct number of chromosomes. “So yes, we have more oocytes that are mature, but at what price if they don’t have the right number of chromosomes?” asked lead author Dr. Cyntia Duval.

Lab Results Reinforce Concerns

In vitro tests added further weight to the findings. When immature eggs were exposed to THC in a lab dish for 24 hours, researchers saw increased abnormalities in the spindles, the tiny structures responsible for separating chromosomes.

These disruptions may lead to failed fertilization or compromised embryo development.

Call for Harm Reduction, Not Panic

“This is a hypothesis, and the worst thing I would want is for the public to read this and become fearful,” Duval emphasized. Dr. Lo echoed that, noting the study could support harm-reduction strategies for those unable to abstain.

“With this information, these patients can consider reducing the amount of cannabis that they are using to mitigate adverse outcomes to their babies.”

THC Potency Is on the Rise

One challenge for users is knowing exactly how much THC they’re consuming. The National Institute on Drug Abuse reports that average THC potency has quadrupled since the mid-1990s.

In today’s market, products, especially extracts, often exceed 40% THC, making it easy to consume far more than intended.

Labels Aren’t Always Reliable

“People buying cannabis illegally may not be able to access reliable information about the potency of the product they are using,” said Tom Freeman, a psychology professor at the University of Bath.

Even legal users may misjudge potency, as efforts to compensate, like using less or inhaling more lightly, don’t fully offset the stronger effects.

Doctors Advise Alternative Remedies

“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,” said Dr. Lo.

She recommends reducing cannabis use where possible, especially for women trying to conceive or who may already be pregnant.