Overview

• The peer-reviewed Nature Communications study combined retrospective follicular-fluid testing from 1,059 IVF patients (6% THC positive) with in vitro exposure of donated immature human oocytes.
• Laboratory exposure to THC was associated with faster nuclear maturation yet more chromosome-segregation errors and atypical meiotic spindles.
• Complex aneuploidy and spindle abnormalities increased with THC exposure, including 42% complex aneuploidy in exposed oocytes versus 0% in controls and 92% abnormal spindles at high dose versus 42% in controls.
• In matched clinical analyses, THC-positive patients had a lower proportion of chromosomally normal embryos compared with THC-negative controls (60.0% vs 67.0%).
• Researchers and outside experts emphasize limits on causal inference due to the small THC-positive subgroup, retrospective design, missing dose and frequency data, and use of immature stimulated-cycle oocytes, and they call for larger prospective, dose–response studies; 73% of THC-positive patients had not disclosed use.