title: Blastocyst culture and cryopreservation to optimize clinical outcomes of warming cycles.
abstract: Surplus embryos available for cryopreservation in fresh cycles are considered as having good potential for future use. However, the optimal stage of embryo cryopreservation remains unclear. In this study, 1190 patients with surplus embryos on day 3 were divided into two groups: cleavage-stage embryo cryopreservation (control group) and blastocyst cryopreservation (blastocyst group). The clinical outcomes of the subsequent warming cycles were evaluated. The proportion of cycles with blastocyst formation was 73.8% in the blastocyst group. Although in the blastocyst group, the cancellation rate of blastocyst transfer was increased due to lack of blastocysts available for cryopreservation, the blastocyst group achieved significantly higher rates of clinical pregnancy/cycle (43.2% versus 34.9%; P=0.003), pregnancy/transfer (59.5% versus 35.4%; P<0.001) and implantation (46.5% versus 22.2%; P<0.001) from the first warming cycle compared with the control group. In an embryo-number classified analysis, the clinical pregnancy rate was also higher in the blastocyst group. However, the cumulative pregnancy was similar between the two groups. Blastocyst culture as an embryo selection tool will not improve embryo viability but it will help patients to achieve pregnancy more quickly. Extended culture of surplus embryos to the blastocyst stage for cryopreservation optimizes the clinical outcomes.
authors.affiliation: Reproductive Medicine Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, PR China.
authors.forename: Lixia
authors.initials: L
authors.lastname: Zhu
authors.forename: Qingsong
authors.initials: Q
authors.lastname: Xi
authors.forename: Hanwang
authors.initials: H
authors.lastname: Zhang
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Li
authors.forename: Jihui
authors.initials: J
authors.lastname: Ai
authors.forename: Lei
authors.initials: L
authors.lastname: Jin
mesh_terms: D000328:Adult; D001755:Blastocyst / Q000473:pathology*; D002681:China / Q000453:epidemiology; D002970:Cleavage Stage, Ovum / Q000473:pathology; D015331:Cohort Studies; D015925:Cryopreservation; D004477:Ectogenesis; D046149:Embryo Culture Techniques; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro; D005500:Follow-Up Studies; D006358:Hot Temperature; D006801:Humans; D007247:Infertility, Female / Q000628:therapy*; D010062:Ovulation Induction; D011247:Pregnancy; D018873:Pregnancy Rate; D020554:Sperm Injections, Intracytoplasmic; D058989:Vitrification
keywords: IVF; blastocyst; cleavage-stage embryo; cryopreservation; vitrified–warmed embryo transfer