POOR-QUALITY FRESH AND FROZEN-THAWED HUMAN CLEAVAGE EMBRYOS MAY HAVE A CLINICAL POTENTIAL AFTER AN EXTENDED CULTURE

In many clinics for Assisted Reproductive Technology (ART) cleavage stage embryos are discarded prior to subsequent transfer (ET) and/or cryopreservation for a low morphological score. The aim of this study was to assess the morphology and viability of fresh and frozen-thawed human cleavage embryos, discarded at the 2nd day of in vitro culture and cultured for further 3 days. Discarded embryos (123) from 57 infertile patients were cultured for 3 days. Their morphology was daily examined. Zona pellucida (ZP) birefringence, assessed by Polscope, and cell viability, by Hoechst/propidium iodide staining, were evaluated at the 5th day. Top-quality expanded blastocysts successfully developed by poor-quality embryos from both fresh and frozen-thawed embryos. However, a normal ZP birefringence was significantly higher in fresh than in frozen-thawed embryos. Discarded embryos were able to grow up to 5 days, with aviability rate of 60.9%. In addition, the viability rate in fresh embryos was significantly higher than frozenthawed ones. In conclusion, poor-quality embryos were capable to develop to the blastocyst stage following an extended culture in vitro, thus representing an alternative choice for clinical applications