Abstract: ObjectiveTo evaluate outcomes from frozen embryo transfer when embryos are frozen on day 3 based on Graduated Embryo Score (GES) or day 5-6 based on expanded blastocyst formation.DesignProspective, randomized.Materials and methodsSetting: Private practice. Patients: Women undergoing frozen embryo transfer with a normal uterine cavity between 1/04-1/06 (n=76). All oocytes were produced by women less than age 40. Interventions: Patients were prospectively randomized in the fresh cycle to have excess embryos beyond those transferred, cryopreserved on day 3 based on GES (Group 1; n=33) or cryopreserved on day 5-6 based on development to the expanded blastocyst stage (Group 2; n=43), which is our current standard. Blastocysts were frozen on day 6 using a slow freeze. Main Outcome Measures: Pregnancy and implantation rates.ResultsTo date 130 patients have been enrolled in the study. Of these 64 (49%) conceived in the fresh cycle. Only those who did not conceive in the fresh cycle (n=76), and only the first FET attempt for each patient was included. The day 3 FET group had more embryos transferred than the day 5-6 group (3.3 versus 2.5, respectively). Pregnancy rates were similar between day 3 FET: (19/33; 58%) and day 5-6 FET: (23/43; 53%). However ongoing pregnancy rates at 8 weeks were significantly higher in the day 3 FET group (15/33; 45%; 4 twins, 2 triplets) compared to day 5-6 FET (7/43; 15%, 2 twins, 4 SAb, 1 ectopic). Implantation rates showed a trend toward day 3 FET (23%) versus day 5-6 FET (13%).ConclusionOutcomes from day 3 FET met or exceeded those of day 5-6 FET when the embryos were selected for freezing on day 3 based on GES. Since as many s 40% of expanded blastocysts are reported to be genetically abnormal, mere survival to blastocyst stage may not be as good a prognosticator of outcome as achievement of early developmental milestones in the fresh cycle. A larger cohort will be needed to fully validate these findings. ObjectiveTo evaluate outcomes from frozen embryo transfer when embryos are frozen on day 3 based on Graduated Embryo Score (GES) or day 5-6 based on expanded blastocyst formation. To evaluate outcomes from frozen embryo transfer when embryos are frozen on day 3 based on Graduated Embryo Score (GES) or day 5-6 based on expanded blastocyst formation. DesignProspective, randomized. Prospective, randomized. Materials and methodsSetting: Private practice. Patients: Women undergoing frozen embryo transfer with a normal uterine cavity between 1/04-1/06 (n=76). All oocytes were produced by women less than age 40. Interventions: Patients were prospectively randomized in the fresh cycle to have excess embryos beyond those transferred, cryopreserved on day 3 based on GES (Group 1; n=33) or cryopreserved on day 5-6 based on development to the expanded blastocyst stage (Group 2; n=43), which is our current standard. Blastocysts were frozen on day 6 using a slow freeze. Main Outcome Measures: Pregnancy and implantation rates. Setting: Private practice. Patients: Women undergoing frozen embryo transfer with a normal uterine cavity between 1/04-1/06 (n=76). All oocytes were produced by women less than age 40. Interventions: Patients were prospectively randomized in the fresh cycle to have excess embryos beyond those transferred, cryopreserved on day 3 based on GES (Group 1; n=33) or cryopreserved on day 5-6 based on development to the expanded blastocyst stage (Group 2; n=43), which is our current standard. Blastocysts were frozen on day 6 using a slow freeze. Main Outcome Measures: Pregnancy and implantation rates. ResultsTo date 130 patients have been enrolled in the study. Of these 64 (49%) conceived in the fresh cycle. Only those who did not conceive in the fresh cycle (n=76), and only the first FET attempt for each patient was included. The day 3 FET group had more embryos transferred than the day 5-6 group (3.3 versus 2.5, respectively). Pregnancy rates were similar between day 3 FET: (19/33; 58%) and day 5-6 FET: (23/43; 53%). However ongoing pregnancy rates at 8 weeks were significantly higher in the day 3 FET group (15/33; 45%; 4 twins, 2 triplets) compared to day 5-6 FET (7/43; 15%, 2 twins, 4 SAb, 1 ectopic). Implantation rates showed a trend toward day 3 FET (23%) versus day 5-6 FET (13%). To date 130 patients have been enrolled in the study. Of these 64 (49%) conceived in the fresh cycle. Only those who did not conceive in the fresh cycle (n=76), and only the first FET attempt for each patient was included. The day 3 FET group had more embryos transferred than the day 5-6 group (3.3 versus 2.5, respectively). Pregnancy rates were similar between day 3 FET: (19/33; 58%) and day 5-6 FET: (23/43; 53%). However ongoing pregnancy rates at 8 weeks were significantly higher in the day 3 FET group (15/33; 45%; 4 twins, 2 triplets) compared to day 5-6 FET (7/43; 15%, 2 twins, 4 SAb, 1 ectopic). Implantation rates showed a trend toward day 3 FET (23%) versus day 5-6 FET (13%). ConclusionOutcomes from day 3 FET met or exceeded those of day 5-6 FET when the embryos were selected for freezing on day 3 based on GES. Since as many s 40% of expanded blastocysts are reported to be genetically abnormal, mere survival to blastocyst stage may not be as good a prognosticator of outcome as achievement of early developmental milestones in the fresh cycle. A larger cohort will be needed to fully validate these findings. Outcomes from day 3 FET met or exceeded those of day 5-6 FET when the embryos were selected for freezing on day 3 based on GES. Since as many s 40% of expanded blastocysts are reported to be genetically abnormal, mere survival to blastocyst stage may not be as good a prognosticator of outcome as achievement of early developmental milestones in the fresh cycle. A larger cohort will be needed to fully validate these findings.