Does the duration of embryo cryo-storage have an impact on clinical, obstetrical and perinatal outcomes following an in vitro fertilization cycle?

This is the question that the latest scientific study published by the GeneraLife group in the RBMO (Reproductive BioMedicine Online) journal and presented at the recent Eshre 2021 congress tried to answer.

The observational study considered 2,688 transfers of single vitrified euploid blastocysts conducted in an IVF center between May 2013 and March 2020. 1,884 patients who underwent at least one transfer after preimplantation genetic test for aneuploidies (PGT-A). The transferred euploid blastocysts were grouped into 7 groups based on the duration of cryo-storage between vitrification and thawing: ≤60 days (N = 646; control group), 61-90 days (N = 599), 91-180 days (N = 679), 181-360 days (N = 405), 361-720 days (N = 144), 721-1080 days (N = 118) and> 1080 days, therefore approximately 3 years (N = 97).

The main indicator was the rate of live births per transfer. The secondary outcomes taken into consideration are the rate of spontaneous abortion, obstetric and perinatal problems. As a result, a significantly lower live birth rate was reported for transfers performed within 91-180 days (N = 291/679, 42.9%), 181-360 days (N = 169/405, 41.7 %) and 361-720 days (N = 57/144, 39.6%) versus ≤60 days (N = 319/646, 49.4%). However, the authors explain, this is mainly due to the fact that, when more euploid blastocysts are available, high-quality embryos are transferred first, leaving the lower-quality ones for subsequent procedures. “In general, the indicators adjusted for all confounders showed similar results across all cryo-storage duration clusters. No differences were also reported for all secondary outcomes. In conclusion, therefore, the duration of cryopreservation even beyond 3 years from the vitrification of the blastocyst does not affect the clinical, obstetric and perinatal outcomes”, says the first author of the paper, Danilo Cimadomo, Science and Research manager of GeneraLife group.