Risk of Contamination of Gametes and Embryos during Cryopreservation and Measures to Prevent Cross-Contamination

The introduction and widespread application of vitrification are one of the most important achievements in human assisted reproduction techniques (ART) of the past decade despite controversy and unclarified issues, mostly related to concerns about disease transmission. Guidance documents published by US Food and Drug Administration, which focused on the safety of tissue/organ donations during Zika virus spread in 2016, as well as some reports of virus, bacteria, and fungi survival to cryogenic temperatures, highlighted the need for a review of the way how potentially infectious material is handled and stored in ART-related procedures. It was experimentally demonstrated that cross-contamination between liquid nitrogen (LN2) and embryos may occur when infectious agents are present in LN2 and oocytes/embryos are not protected by a hermetically sealed device. Thus, this review summarizes pertinent data and opinions regarding the potential hazard of infectious transmission through cryopreserved and banked reproductive cells and tissues in LN2. Special attention is given to the survival of pathogens in LN2, the risk of cross-contamination, vitrification methods, sterility of LN2, and the risks associated with the use of straws, cryovials, and storage dewars.