Higher success rates in thawed embryo transfer after in vitro culturing following cryopreservation of fresh embryos

Abstract

OBJECTIVE: It is well known that transfer of cryopreserved-thawed embryos during a natural or a programmed cycle yields an excellent pregnancy rate. We therefore cryopreserved all embryos two days after oocyte retrieval, thawed them when needed, and then maintained them in an in-vitro culture for one day prior to uterine transfer.DESIGN: Retrospective clinical analysis of 564 cycles in 395 patients who received either thawed or fresh embryos.MATERIALS AND METHODS: Thawed embryo transfer (T) in 172 cycles (114 patients) and fresh embryo transfer (F) in 392 cycles (281 patients) randomly allocated to treatments with one of 3 kinds of controlled ovarian hyperstimulation methods [GnRH-antagonist + HMG-I, GnRH-agonist + FSH-Short (II'), Long (II'')] (following the ICSI) were analyzed. Thawed embryo transfer (T): All embryos recovered in hormone-stimulated cycles were cryopreserved according to the slow-cooling method (1.8 M ethylene glycol + 0.2 M sucrose) at the 4∼6 cell stage, and then, after thawing, transferred after one day of additional culture. Fresh embryo transfer (F): high quality embryo were transferred 3 days after the oocyte retrieval.RESULTS: The pregnancy and miscarriage rates in each group were as follows. [T-I: 51.9% (28/54), 17.9% (5/28)], [T-II': 56.4% (53/94), 9.4% (5/53)], [T-II'': 41.7% (10/24), 30.0% (3/10)], [F-I: 40.3% (50/124), 26.0% (13/50)], [F-II': 30.5% (72/236), 16.7% (12/72)], [F-II'': 43.8% (14/32), 21.4% (3/14)].CONCLUSIONS: The clinical success rates following the thawed embryo transfer were higher than those following the fresh embryo transfer in each COH method and was significantly higher in the group using GnRH-agonist-Short protocol. We believe that cryopreserving all embryos that are produced from the initial batch of collected oocytes and then transferred during the natural cycle will provide the best chance of a successful pregnancy. OBJECTIVE: It is well known that transfer of cryopreserved-thawed embryos during a natural or a programmed cycle yields an excellent pregnancy rate. We therefore cryopreserved all embryos two days after oocyte retrieval, thawed them when needed, and then maintained them in an in-vitro culture for one day prior to uterine transfer. DESIGN: Retrospective clinical analysis of 564 cycles in 395 patients who received either thawed or fresh embryos. MATERIALS AND METHODS: Thawed embryo transfer (T) in 172 cycles (114 patients) and fresh embryo transfer (F) in 392 cycles (281 patients) randomly allocated to treatments with one of 3 kinds of controlled ovarian hyperstimulation methods [GnRH-antagonist + HMG-I, GnRH-agonist + FSH-Short (II'), Long (II'')] (following the ICSI) were analyzed. Thawed embryo transfer (T): All embryos recovered in hormone-stimulated cycles were cryopreserved according to the slow-cooling method (1.8 M ethylene glycol + 0.2 M sucrose) at the 4∼6 cell stage, and then, after thawing, transferred after one day of additional culture. Fresh embryo transfer (F): high quality embryo were transferred 3 days after the oocyte retrieval. RESULTS: The pregnancy and miscarriage rates in each group were as follows. [T-I: 51.9% (28/54), 17.9% (5/28)], [T-II': 56.4% (53/94), 9.4% (5/53)], [T-II'': 41.7% (10/24), 30.0% (3/10)], [F-I: 40.3% (50/124), 26.0% (13/50)], [F-II': 30.5% (72/236), 16.7% (12/72)], [F-II'': 43.8% (14/32), 21.4% (3/14)]. CONCLUSIONS: The clinical success rates following the thawed embryo transfer were higher than those following the fresh embryo transfer in each COH method and was significantly higher in the group using GnRH-agonist-Short protocol. We believe that cryopreserving all embryos that are produced from the initial batch of collected oocytes and then transferred during the natural cycle will provide the best chance of a successful pregnancy.