Vitrification of blastocysts derived from fair to poor quality cleavage stage embryos can produce high pregnancy rates after warming.

ABSTRACT

PURPOSE: This study investigates whether certain embryos considered unsuitable for cryopreservation on day 3 might nevertheless have the potential to develop into worthwhile blastocysts that could be vitrified in the same cycle. METHODS: Retrospective study between 2010 and 2011, embryo transfers and cryopreservation took place mainly on day 3 in our centre. Supernumerary embryos of intermediate to poor quality were reassessed on days 5/6 and any good quality blastocysts were vitrified. RESULTS: Out of 914 cleavage stage (day 3) embryos left in culture, 16 % were vitrified on days 5/6. Fifty blastocyst warming cycles resulted in a 76 % survival rate, 44 % clinical pregnancy rate and 39 % implantation rate. During the same time period, 213 warming cycles of good quality cleavage stage embryos rendered survival rates, clinical pregnancy and implantation rates of 97 %, 23 % and 16 % respectively. CONCLUSIONS: Supernumerary average quality day 3 embryos should be given a second chance to be selected for cryopreservation. If blastocysts are obtained and survive vitrification, there is a good chance of implantation thus reducing embryo waste.