Results of double freezing approach in the management of surplus embryos in IVF

Introduction: transfer of thawed embryos is gaining more popularity in IVF treatments mainly due to improvement in gamete cryopreservation techniques and the willing to reduce multiple pregnancies.
Aim: to retrospectively evaluate pregnancy rates of IVF cycles in whom surplus thawed cleaved embryos (day 2 or 3) were grown to the blastocyst stage, re-frozen and then later re-thawed for transfer.
Material and Methods: all consecutive women during a 5-year period in whom surplus thawed cleaved embryos (day 2 and 3) were grown to the blastocyst stage, re-frozen and then later re-thawed for transfer. The control group consisted of patients undergoing frozen- thawed blastocyst transfer in the same study period, matched by age in 2:1 ratio.
Results: fifty four patients had 70 embryos that were re-frozen at the blastocyst stage. Twenty-eight of these blastocysts were thawed and underwent transfer to 25 patients (study group). The survival rate of the second thawing was 96.4% (27/28). Clinical pregnancy rate was 16% (4/25) and implantation rate was 14.8% (4/27). Twenty two of the 25 patients in the study group conceived in IVF treatment at our IVF unit either before or after the re-frozen transfer indicating good receptivity of the uterus in these patients. During the same study period, 50 patients (control group) underwent a single thawed blastocyst transfer. The implantation/pregnancy rates were significantly higher [44.2% (23/52)], as compared to the study group. The outcome in the control group confirm the efficacy of our laboratory blastocyst freezing-thawing technique.
Conclusion(s): Transfer of twice-frozen-thawed embryos is feasible and adds to the cumulative pregnancy rate of an IVF cycle. However, pregnancy rate of these embryos seems to be lower compared to once frozen thawed embryos.