Assessment of a double freezing approach in the management of surplus embryos in IVF.

Abstract

What pregnancy rates are achieved after transfer of cryopreserved double slow-frozen embryos in IVF cycles? Patients in whom surplus thawed cleaved embryos (day 2 or 3) were grown to the blastocyst stage, re-frozen and then re-thawed for transfer (double freezing) were included. Data were collected on all patients who had undergone the above procedure at the IVF unit of Assuta Ramat Hachayal Hospital, Tel Aviv, during a 7-year period. For each patient in the study group, the two-consecutive, matched-by-age patients treated with frozen-thawed single blastocyst transfer were selected to form a 2:1 ratio control group. All embryos were frozen using the slow freeze protocol. A total of 54 patients had 70 embryos that were re-frozen at the blastocyst stage. Twenty-eight of these blastocysts were thawed and 27 underwent transfer to 25 patients. A single embryo was transferred to 23 patients and two embryos were transferred to two patients. 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). In the study group, pregnancies were achieved in 22 out of the 25 patients using IVF treatment, indicating good receptivity of the uterus. In the control group, the implantation/pregnancy rates were significantly higher (44.2% [23/52]; P < 0.01). The transfer of twice slow-frozen and thawed embryos does not seem to be a beneficial approach in the planned management of cryopreserved surplus embryos owing to the low pregnancy rate achieved after transfer of the re-frozen blastocyst embryos.