Type of publication:
*Binnersley S.; *Hughes G.; *Hatton A.; *Gittins V.; *Kasraie J.
Human Fertility; 2013; vol. 16 (no. 3)
Introduction : Conservation of viable embryos minimises risk to patients from repeated stimulation/egg collection, reduces costs and maximises cumulative success rates, but national practice varies greatly. Many clinics only cryopreserve top quality embryos, potentially leading to the disposal of viable embryos and unnecessary further cycles of IVF. Our clinics experience of survival rates from traditional ‘slow’freezing, where fragmentation may provide additional foci for ice crystal formation, meant that, when our clinic introduced Vitrification in 2008, we continued to cryopreserve only embryos with < 5% fragmentation. However survival and pregnancy rates using vitrification were such that from May 2010, following validation of survival rates, criteria were relaxed to allow embryos with 15% fragmentation to be stored. Materials and Methods: Retrospective analysis of 156 frozen (vitrified) embryo transfer cycles. Embryos were classified as top (<=5% fragmentation) or non-top (5 to 15% fragmentation) quality. Two embryos were transferred in all cycles. Three groups were compared: 1 < Two top quality (n=109), 2=One top and one non-top (n=20), 3=two non-top (n=27) quality transferred. Vitrification cooling/warming utilised Origio media and Cryo-Bio system sealed straws. Results: There was no significant difference for patient age (p=0.48), survival rates of blastomeres in each group (97.9% vs 96.7% and 98.1%, p=0.62), biochemical pregnancy rate (36.7% vs 30.0% vs 33.3%, p=0.62), clinical pregnancy rate (20.2% vs 10.0% vs 22.2%, p=0.36), or implantation rate (12.8% vs 5% vs 12.96%, p=0.19) in all groups. Conclusion: This small retrospective study appears to show that vitrication of lower grade embryos (15% fragmentation) results in similar pregnancy rates to the vitrification of only top quality embryos. The resultant increase in the number of stored embryos and frozen embryo transfers decreases risk to the patient and cost to the healthcare economy whilst increasing the cumulative pregnancy rate from single ‘fresh’IVF cycles