Comparison of the clinical outcomes between fresh blastocyst and vitrified-thawed blastocyst transfer

To compare the clinical outcomes between fresh and vitrified-thawed day 5 blastocyst transfers. Retrospective case control study. Tertiary referral center. Patients 38 years of age or less who underwent IVF/ICSI cycles with fresh or frozen-thawed blastocysts transferred from June 1, 2009 to November 30, 2011 Vitrification and thawing of day 5 blastocysts using the Cryotop method. (Kitazato BioPharma Co., Ltd., Fuji city, Shizuoka, Japan) Clinical pregnancy rate, implantation rate, ongoing pregnancy rate, and multiple pregnancy rates. Of the 118 cycles in the fresh transfer group, 234 blastocysts were transferred. The clinical pregnancy rate was 66.1 % and implantation rate was 50.9 %. The ongoing pregnancy rate was 56.8 % and the rates for singleton and twin pregnancies were 53.7 % and 44.8 %. Of the 59 cycles in the vitrified-thawed group, 111 blastocysts were transferred. The clinical pregnancy rate was 59.3 % and implantation rate was 43.2 %. The ongoing pregnancy rate was 47.5 % and the rates for singleton and twin pregnancies were 60.7 % and 39.3 %. The clinical pregnancy rate, implantation rate and ongoing pregnancy rate did not differ significantly between the two groups. The implantation rates were not significantly different between the fresh and the vitrified-thawed groups. Thus, single embryo transfer may be considered in fresh cycles to decrease multiple pregnancy rates. The surplus embryos should be vitrified for the frozen embryo transfer to improve the cumulative pregnancy rate.