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A comparison of efficacy of freezing embryos at the 2 pronuclear (2PN) stage vs multi-cell when using a simplified freezing protocol with one-step removal of cryoprotectant
1 The University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School at Camden, Cooper Hospital/University Medical Center, Department of Obstetrics and Gynecology, Division of Reproductive Endocrinology & Infertility, Camden, NJ (USA)
Clin. Exp. Obstet. Gynecol. 2009, 36(4), 210–211;
Published: 10 December 2009
Purpose: To compare the efficacy of freezing embryos at the 2 pronuclear stage vs multi-cell stage using a simplified freezing protocol with a one-step removal of the cryoprotectant. Methods: A retrospective analysis was performed. Survival, delivered pregnancy and implantation rates were compared in transfers of all embryos frozen at 2 pronuclear stage (2PN) or all embryos frozen at multi-cell stage. The results were further stratified and compared according to the number of high quality embryos transferred. Results: In all categories despite comparing similar numbers and quality of embryos transferred there was a significantly higher survival rate of 2PN embryos. Significantly higher delivered pregnancy and implantation rates were seen with 2PN vs multi-cell embryos when there was only one or two embryos with ≥6 blastomeres and <25% fragmentation, and a trend for higher delivered pregnancy rates when there were three top quality embryos transferred. Conclusions: When given the option it is preferable when using this simplified freezing and thawing protocol to freeze at the 2PN stage.
Simplified freezing protocol
2 pronuclear stage