Elective single blastocyst transfer and the cryo-augmentation effect of aseptic vitrification: a comparison of two strategies

Abstract

OBJECTIVE: In IVF treatment cycles, the number of good quality embryos on day 3 often weighs into the decision whether or not to proceed towards blastocyst transfer. This study compares the outcome of two embryo transfer policies: (1) single blastocyst transfer irrespective of day 3 embryo evaluation versus (2) single blastocyst transfer only if at least 4 good quality embryos are available on day 3. DESIGN: A retrospective review of 590 IVF cycles with patients grouped based on whether a day 5 transfer was planned (n=341) or day 5 transfer depended on a day 3 evaluation (n=249). MATERIALS AND METHODS: Blastocyst vitrification was performed with the closed CBS high security straws. No differences were observed in the age, rank of trial, days of stimulation and total gonadotropin dose. Neither was there a difference observed in total number of cumulus-oocyte complexes, MII oocytes or 2PN oocytes. RESULTS: Patients in the planned day 5 group have a lower subjects' fresh transfer rate (90.62 vs. 95.18% p<0.05) but no difference was seen in the fresh live birth and multiple pregnancy rates per initiated cycle (32.84 vs. 28.92%; 1.17 vs. 0%). Warmed blastocyst cycles of the planned day 5 group resulted in a similar transferable survival rate as blastocysts in the day 3 or day 5 group (69.9 vs. 76.5%). For thawing cycles, SET was equally performed in both strategies (87 vs. 78.05%). The projected cumulative ongoing pregnancy rate compensating for double counting in case subjects have more than one pregnancy is not different (42.58% vs. 39.84%). CONCLUSION: Elective day 5 transfer and aseptic vitrification offers an excellent ongoing pregnancy rate of 42.58%. Despite better fresh transfer rates, a transfer policy based on day 3 embryo evaluation does not affect the cumulative pregnancy rate.