THC linked to chromosomal abnormalities in IVF eggs and embryos

Researchers in Toronto reported Tuesday that exposure to tetrahydrocannabinol, or THC, the main psychoactive ingredient in cannabis, was linked to more chromosomal abnormalities in human eggs and early embryos and to lower rates of chromosomally normal embryos in patients undergoing in vitro fertilization. The findings, published in Nature Communications, come from two complementary analyses: laboratory experiments on immature oocytes and a retrospective comparison of follicular fluid from IVF patients.

The research team, led by Cyntia Duval of the CReATe Fertility Centre and affiliated with the University of Toronto, measured THC and its metabolites directly in follicular fluid collected during IVF. The investigators screened 1,059 samples and found cannabis metabolites in 62. In the clinical comparison, cycles with THC detected in follicular fluid had a lower embryo euploidy rate than matched cycles without detectable THC. In parallel laboratory experiments, immature oocytes exposed to THC showed a rise in aneuploidy, or incorrect chromosome number, and more frequent spindle abnormalities, cellular defects that interfere with proper chromosome segregation. The team also...