The new Rapid-i carrier is an effective system for human embryo vitrification at both the blastocyst and cleavage stage

BACKGROUND The Rapid-i is a new FDA cleared closed carrier for embryo vitrification. The cooling rate of - 1220°C/min is far lower than that reported with open vitrification systems such as the cryoloop (-15,000°C/min). Little published data is currently available on this device. This study presents our initial clinical data, as well as live birth outcomes, with the Rapid-i. The efficacy of this device for the cryopreservation of cleavage, as well as blastocyst stage human embryos is also analyzed. We further compare outcomes to those achieved with the cryoloop, an "open" vitrification system routinely used in our laboratory. METHODS Human embryos were vitrified at either the 8-10 cell stage or else the blastocyst stage. The vitrification protocol was: 7.5% DMSO/7.5% ethylene glycol (EG) (2-3 min) followed by incubation in 15% DMSO /15% EG (45 sec) before loading on the vitrification carrier. Cryoprotectant was removed during warming by sequential washes in 0.25 M and 0.125 M sucrose in culture medium. Clinical outcome data for frozen cycles between January 2011 and August 2012 were stratified according to carrier and cell stage. The student t-test and chi square test were used to compare results. P value of < 0.05 was considered significant. RESULTS A total of 486 vitrified-warmed embryos were assessed and 92% of them were transferred. The clinical pregnancy rate (CPR) and implantation rate (IR) with Rapid-i vitrified blastocysts were 59% and 49%, versus 47% and 37%, respectively for cleavage stage embryos. This was not statistically different from results with the cryoloop vitrified blastocysts (CPR 46%, IR 38%) nor the cleavage stage vitrified embryos (CPR 49%, IR 35%). To date, there have been 31 deliveries of 34 healthy infants from Rapid-i vitrified embryos, with another 12 pregnancies still on-going. CONCLUSIONS The Rapid-i offers an excellent alternative to existing open vitrification devices for embryo cryopreservation at the 8-10 cell stage as well as the blastocyst stage. Use of this type of "closed" sealed system that prevents direct contact between the embryos and liquid nitrogen reduces the potential risk of sample cross-contamination or infection. These preliminary data and live birth outcomes have paved the way toward transitioning to a closed vitrification system in our own IVF program.