Vitrified-thawed single blastocyst transfer (vSBT) reduces the multiple pregnancy rate compared with vitrified-thawed double blastocyst transfer (vDBT) without compromising IVF outcomes

Abstract

OBJECTIVE: We determined criteria for elective single blastocyst transfer (eSBT) using fresh balstocysts as; (1) more than two 3AA or higher blastocysts, (2) age less than 36 years, and (3) less than three failed embryo transfer cycles. To reduce multi-pregnancies, it was crucial to apply the SBT policy to fresh cycles as well as to cryopreserved-thawed ones. We also investigated whether vSBT compromised outcomes of our IVF protocol compared with fresh SBT (fSBT) and vDBT.DESIGN: Retrospective study.MATERIALS AND METHODS: We analyzed 209 fresh IVF/ICSI and vitrified-thawed blastocyst transfer cycles. We offered eSBT to patients before oocyte retrieval. Fertilized oocytes were cultured in sequential medium for 5 days and each embryo evaluated by the Gardner's criteria. For patients not under the eSBT policy, one or two embryos, if they were morula or a higher blastocyst, were transferred. Surplus 3BB or higher blastocysts were cryopreserved by vitrification. When no embryo developed to 3BB or higher blastocysts at day 5, lesser grade blastocysts were vitrified if the patient chose. We proffered our SBT policy even for vitrified-thawed transfer cycles when two or more 3BB or higher blastocysts were available. Compulsory SBT was performed if just one blastocyst was available. Overall, 111 cycles underwent SBT (40 thawed, 71 fresh) and 41 underwent vDBT. Clinical outcomes of vSBT were compared with those of vDBT and fSBT. Clinical pregnancy was defined as a positive serum hCG test and a sac seen on an ultrasound scan. Statistical analysis was performed using χ-square methods. p<0.05 was considered significant.RESULTS: vSBT, vDBT and fSBT groups had similar patient ages and other demographic characteristics. Overall clinical pregnancy, miscarriage, and multiple pregnancy rates for vSBT were similar to those of fSBT; 43% vs. 32%, 18% vs. 22%, 0% vs. 0%, respectively. Clinical pregnancy and miscarriage rates for vSBT were similar to vDBT; 59%, 42%, 29%, respectively. The multiple pregnancy rate for vSBT compared with vDBT was significantly reduced (0% vs. 29%: p<0.05). A significantly high clinical pregnancy rate was achieved following the transfer of vitrified-thawed single 3BB or higher blastocysts compared with lesser grade ones (53.3% vs. 10%; p<0.05).CONCLUSIONS: vSBT offers good outcomes for an IVF protocol. When good quality blastocysts are available, the number of embryos transferred does not need to increase and multiple pregnancies can be reduced even in vitrified-thawed transfer cycles. OBJECTIVE: We determined criteria for elective single blastocyst transfer (eSBT) using fresh balstocysts as; (1) more than two 3AA or higher blastocysts, (2) age less than 36 years, and (3) less than three failed embryo transfer cycles. To reduce multi-pregnancies, it was crucial to apply the SBT policy to fresh cycles as well as to cryopreserved-thawed ones. We also investigated whether vSBT compromised outcomes of our IVF protocol compared with fresh SBT (fSBT) and vDBT. DESIGN: Retrospective study. MATERIALS AND METHODS: We analyzed 209 fresh IVF/ICSI and vitrified-thawed blastocyst transfer cycles. We offered eSBT to patients before oocyte retrieval. Fertilized oocytes were cultured in sequential medium for 5 days and each embryo evaluated by the Gardner's criteria. For patients not under the eSBT policy, one or two embryos, if they were morula or a higher blastocyst, were transferred. Surplus 3BB or higher blastocysts were cryopreserved by vitrification. When no embryo developed to 3BB or higher blastocysts at day 5, lesser grade blastocysts were vitrified if the patient chose. We proffered our SBT policy even for vitrified-thawed transfer cycles when two or more 3BB or higher blastocysts were available. Compulsory SBT was performed if just one blastocyst was available. Overall, 111 cycles underwent SBT (40 thawed, 71 fresh) and 41 underwent vDBT. Clinical outcomes of vSBT were compared with those of vDBT and fSBT. Clinical pregnancy was defined as a positive serum hCG test and a sac seen on an ultrasound scan. Statistical analysis was performed using χ-square methods. p<0.05 was considered significant. RESULTS: vSBT, vDBT and fSBT groups had similar patient ages and other demographic characteristics. Overall clinical pregnancy, miscarriage, and multiple pregnancy rates for vSBT were similar to those of fSBT; 43% vs. 32%, 18% vs. 22%, 0% vs. 0%, respectively. Clinical pregnancy and miscarriage rates for vSBT were similar to vDBT; 59%, 42%, 29%, respectively. The multiple pregnancy rate for vSBT compared with vDBT was significantly reduced (0% vs. 29%: p<0.05). A significantly high clinical pregnancy rate was achieved following the transfer of vitrified-thawed single 3BB or higher blastocysts compared with lesser grade ones (53.3% vs. 10%; p<0.05). CONCLUSIONS: vSBT offers good outcomes for an IVF protocol. When good quality blastocysts are available, the number of embryos transferred does not need to increase and multiple pregnancies can be reduced even in vitrified-thawed transfer cycles.