Pronuclear embryo cryopreservation experience: outcomes for reducing the risk of ovarian hyperstimulation syndrome and for fertility preservation in cancer patients

Purpose To evaluate pregnancy rate (PR) and live birth rate (LBR) after freezing pronuclear (PN) embryos for two purposes: to reduce the risk of ovarian hyperstimulation syndrome (OHSS) and to bank embryos for cancer patients anticipating gametotoxic chemotherapy/radiotherapy. Methods Data from 3,621 consecutive IVF cycles were retrospectively analyzed. PN freezing was offered to patients at risk for OHSS and for those wishing to preserve fertility prior to cancer therapy. Primary outcomes evaluated were PR and LBR. Outcomes were compared to patients who underwent fresh embryo transfer (ET) in 2006. Results Sixty-six patients froze PN embryos. Thirty-eight were at risk for OHSS. The LBR was 34.3% after one transfer, and 51.4% after a mean of 1.4 transfers. Twenty-eight cancer patients froze embryos. The LBR was 16.7% after one transfer and 25.0% after a mean of 1.5 transfers. The LBR was 35.5% for patients who underwent fresh ET. Conclusion PN freezing with delayed ET is an effective tool for achieving pregnancy for patients at risk of OHSS and for cancer patients wishing to preserve fertility.