Marijuana may cause chromosomal defects in human egg cells, study finds
By Sandee LaMotte, CNN September 9, 20251/2
Marijuana may damage oocytes — unfertilized eggs in female ovaries — in ways researchers”worry” may leadto infertility, miscarriage and possible genetic defects in babies, new research has found.
==Higher levels of tetrahydrocannabinol, or THC — a chemical in marijuana
that produces a euphoric feeling or “high” — was linked with changes in how eggs mature and a possible increase in chromosome malformations==, according to the study published Tuesday in the journal Nature Communications.
“The findings of this study are concerning and highlight the importance of a cautious approach in using cannabis when planning to conceive,” said obstetrician Dr. Jamie Lo, an associate professor of obstetrics, gynecology and urology in the School of Medicine at Oregon Health & Science University in Portland, in an email. She was not involved with the study.
Use of marijuana during pregnancy is rising. A June study found past-monthself-reported cannabis use has more than tripled among pregnant womenin the United States from 2002 to 2020. Numerous studies have linked marijuana use during pregnancy to autism, poor fetal development, low infant birth weight, dangerously early deliveries and even death.
The new study is “an exciting and novel approach to address a key gap in knowledge,” said Lo, who studies marijuana and fertility. A number of studies have looked at how marijuana might affect sperm, but until now no study had looked at the impact of marijuana on the human egg and ovarian follicle, she said.
A follicle is a small, fluid-filled sac in the ovary that contains one unfertilized egg. During a woman’s menstrual cycle, hormones kick off a chain of events that help the oocyte segregate chromosomes so it will be ready for fertilization by sperm.
Higher levels of THC appeared to impact this process, said lead study author Cyntia Duval, who conducted the study while a postdoctoral research fellow in ovarian biology at the University of Toronto.
However, the study can only show an association and not a direct cause and effect, said Duval, who nowdirects applied research at CReATe Fertility Centre, a fertility clinic in Toronto. (CReATe stands for Canadian Reproductive Assisted Technology.)(no wonder about them guessing)
“This is a hypothesis, and the worst thing I would want is for the public to read this and become fearful,” she said. “More studies are needed to verify our findings and determine how or even if the changes we observed affect reproduction.”
=Higher levels of THC most harmful
Researchers analyzed over 1,000 ovarian fluid samples from patients undergoing infertility treatment. Oocytes from a smaller group of 62 patients who tested positive for THC were compared with a matched control group with no detectable use of cannabis.
Compared with the control group, the group of patients with detectable levels of THC was associated with an increased oocyte maturation rate and a lower number of embryos with the correct number of chromosomes, the study team found.
On first glance, a higher maturation rate may appear to be positive, but developing too quickly can create problems with how oocytes prepare for reproduction, Duval said.
“Chromosomes need time to align perfectly to be ready to be fertilized by sperm and create healthy embryos,” she said. “So yes, we have more oocytes that are mature, but at what price if they don’t have the right number of chromosomes?”
https://lite.cnn.com/2025/09/09/health/marijuana-female-fertility-study-wellness