Cannabis Might Be Messing With Female Fertility

Cannabis could be risky for women becoming or hoping to become pregnant. New research out today finds evidence that the drug can negatively affect women’s fertility.

Scientists in Canada examined the impacts of cannabis on eggs and embryos from women undergoing in vitro fertilization treatment. They found that greater levels of tetrahydrocannabinol (THC) exposure were linked to several harmful changes, including eggs and embryos with the wrong number of chromosomes. Though it’s unclear exactly how cannabis may affect pregnancy outcomes in the real world, the findings do support current recommendations to avoid its use during pregnancy, the researchers say.

“Collectively, this data presents compelling evidence that cannabis consumption may negatively impact female fertility,” the researchers wrote in their paper, published Tuesday in Nature Communications.

The cannabis connection

Plenty of research has suggested that cannabis and THC, the primary ingredient responsible for the drug’s “high,” can harm men’s fertility. But according to the researchers, there’s been significantly less attention paid to how it might affect women’s reproductive health—an increasingly relevant question given the drug’s growing legalization in the U.S.

The scientists had earlier shown that THC and its byproducts can reach the ovarian follicles, the structures containing an egg that’s eventually released during ovulation. This time, they wanted to get a closer look at THC’s potential effects on a woman’s eggs.

In the lab, they exposed immature oocytes, better known as eggs, collected during IVF treatment to THC and its byproducts (the eggs were deemed waste material, which the patients consented to being used for research). They also conducted a retrospective analysis of IVF patients, comparing women who tested positive for THC exposure in their follicular fluid to closely matched controls who tested negative for it.

After THC exposure in the lab, the team noticed an increase in the number of aneuploid eggs, or eggs with the wrong number of chromosomes. In the retrospective study, they found that IVF patients positive for THC had a lower embryo euploidy rate, or embryos with the correct number of chromosomes. High enough levels of THC also seemed to speed up the maturation of eggs.

Lingering questions

Lead study researcher Cyntia Duval is a postdoctoral fellow at the CReATe Fertility Center in Toronto. She notes that their sample size of IVF patients (62 positive for THC) is too small to truly know if THC can lower a woman’s odds of successful pregnancy. But the findings do suggest that cannabis can have real impacts on the health of a woman’s eggs and embryos.

Duval and her team are still hoping to learn more about the harmful effects of THC and other cannabinoids on women’s fertility. They’re next planning to study how these compounds can affect an egg cell’s epigenetics—how its genes are actually expressed. It’s possible that some epigenetic changes in an egg caused by THC could then be passed along to a resulting embryo.

But she also points out that doctors and health organizations, including the American College of Obstetricians and Gynecologists, already advise women who are or are hoping to become pregnant to stop using cannabis and other recreational drugs. “Our study provides data, showing how cannabinoids can be associated with altered chromosomal segregation in oocytes and embryos,” Duval said.

So while there might be some unanswered questions about THC and women’s fertility, the take-home message appears clear: Women should avoid or at least try to reduce their cannabis use while pregnant or trying to conceive.