The aim of this study was to evaluate if clinical outcomes differ between day 5 blastocyst stage vitrified embryos thawed on the day prior to versus the day of transfer.MATERIALS AND METHODS: Design: Retrospective study.Setting: Academic fertility center.Interventions: Blastocysts vitrified and thawed the day prior to transfer (Group 1) were compared to those thawed the day of transfer (Group 2). All embryos were vitrified on the cryolock device and all patients underwent endometrial priming. Pregnancies were initially detected by serum b-human chorionic gonadotropin (hCG) concentrations. Clinical pregnancy and implantation were confirmed by transvaginal ultrasound (US). Exclusion criteria included: donor oocyte, pre-implantation genetic testing, and gestational carrier cycles, as well as cycles that included embryos imported from different centers and cycles with combined day 5 (D5) and day 6 (D6) frozen embryo transfers.Outcome Measures: Positive pregnancy test (serum b-hCG concentration >6 IU/L) per cryothaw cycle, clinical pregnancy (CPR) and implantation rates (number of sacs observed on US over the number of embryos transferred).Statistics: X 2 -square and t-test were used as appropriate. P<0.05 was considered statistically significant.RESULT(S): A total of 112 thawed blastocysts (88 D5, 24 D6) from 94 patients were included in the analysis. Patient characteristics did not differ between the 2 groups of embryos (Table 1). When all blastocyst stage embryos (D5 and D6) were compared between the Group 1 and Group 2, positive pregnancy test (61.7% vs 70.2, p¼0.51, respectively), CPR (61.7% vs 62.2%, p¼1.00, respectively) and, implantation (85.0% vs 82.4%, p¼0.76, respectively) rates did not differ. When the analysis was restricted to D5 embryos, which were the blastocysts affected by the intervention implemented, positive pregnancy test, CPR and implantation rates were similar amongst the groups (Chart 1). CONCLUSION(S): According to our findings, thawing D5 blastocysts the day prior to transfer does not impact CPR or implantation rates, thus allowing embryologists some flexibility to the timing of D5 embryo thaw.FINANCIAL SUPPORT: none.

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from a second biopsy for each embryo. Phase 2 involved clinical utilization of combined SGD and CCS testing with follow-up.RESULTS: Workup time approximated 1 month for each case. Phase 1 testing examined 152 embryos and demonstrated 99% concordance with reference lab data with all discrepancies confirmed as an error with the reference labs results. Phase 2 involved clinical application of these methods in 43 patients (304 embryos). A definitive result was reported for 99.7% (303/304) embryos, with 0.3% (1/304) having an inconclusive result likely due to recombination. All cases for which a sample was available in a newborn child confirmed the PGD result. In patients receiving a transfer with follow-up, clinical outcomes were excellent with an implantation rate of 75% (12/16), with 92% of patients achieving pregnancy.CONCLUSIONS: This methodology has demonstrated excellent concordance with current methods of SGD and provides a unique opportunity to avoid pitfalls of WGA when targeting additional loci in the genome in parallel with CCS. Additional advantages of the method include the ability to manage microdeletion and duplication cases and the potential for a 4 hour turnaround time. In addition, it is well established that SNP markers are denser than STRs thus generally reducing the distance of markers from mutations and the potential impact of recombination.

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