In recent years several closed vitrification systems have been developed. These systems achieve different cooling and warming rates depending on device design and, in combination with different vitrification and warming solutions, may give different results. A study (abbriviated below) on which vitrification system, Rapid-i (Vitrolife) or CryoTop (Kitazato) that resulted in the best blastocyst viability post warming was presented at ESHRE 2016. The result showed significantly higher survival- and pregnancy rates with Rapid-i™ compared to CryTop®SC.
Material and Methods
This prospective study was ongoing for almost two years. Day 5 blastocysts were vitrified either using Rapid-i (316 blastocysts) or CryTop SC (306 blastocysts). After warming, blastocysts were assessed as survived if >40% of the features were intact. Single blastocyst transfer was employed. The survival, pregnancy and miscarriage rates were compared.
The blastocyst survival rate was significantly higher using Rapid-i, 90.2%, compared to 81.7% with the use of CryoTop SC. (Fig 1) Also the pregnancy rate was significantly higher, 39.9 % and 30.3% with Rapid-i and Cryotop SC, respectively. (Fig 2) The miscarriage rate was numerically lower with Rapid-i but the difference was not statistically significant. (Fig 2).
Fig 1. Survival rate
Fig 2. Pregnancy rates and miscarriage rates
In this prospective study, significantly higher survival rate and pregnancy rate was obtained after vitrification and warming using Rapid-i Vitrification system compared to CryTop SC, both closed vitrification systems.
REF. Utsunomiya T et el., St Luke Clinic, Oita, Japan. Effect ofvitrification-warming cycle at the blastocyst stage using two types of closed vitrification systems. ESHRE, Helsinki, Finland. 2016.