Влияние переносов размороженных бластоцист, экспандированных на пятые или шестые сутки на эффективность программ ВРТ

In order to increase the effectiveness of assisted reproductive technologies (ART) programs, it is essential to improve and develop conditions of embryo culture prior its transfer or cryopreservation of expanded blastocysts on the day 5 or 6. The aim of the study was to assess the effect of human blastocysts’ expansion timing on clinical pregnancy rate (CPR), miscarriage rate (MR) and take-home baby rate (THBR) in frozen-thawed cycles during ART programs. The study involved 2275 frozen embryo transfers (FET) of blastocysts expanded on the day 5 (group A) and 170 FET of blastocysts expanded on the day 6 (group B). The pregnancy rates in both groups were 50.8% and 46.5% respectively. There were no statistically significant differences in clinical pregnancy rate 37.4% and 37.0%, miscarriage rate 26.0% and 21.5% in both groups, respectively. THBR, as the main indicator of efficiency in the programs with transfer of post thawed expanded blastocysts on the day 5 (group A) or 6 (group B) were 36.5% and 35.2%, respectively (the difference is insignificant). In conclusion, in cryoprotocols the day of blastocyst expansion (day 5 or 6 of development) does not statistically affect PR, MR and THBR. In FET programs the quality of blastocyst (excellent and good) should be prioritized regardless of the day of cryopreservation.