successful pregnancy following the transfer of vitrified blastocyst which developed from poor quality embryos on day 3

background: the selection of pre-embryos for transferred is based on morphological appearance. but some poor quality cleaved embryos also can be cultured to the blastocyst stage and implanted. objective: to assess the clinical pregnancy outcomes of blastocyst transfer which developed from poor quality embryos. materials and methods: a total of 109 cleaved embryos with poor quality were cultured to day 5/day 6 and 27 (24.8%) blastocysts were collected from the 15 cycles/patients undergoing conventional ivf. all the blastocysts were cooling with fast-freezing. then the blastocysts were warmed for transfer. results: all of 25 vitrified blastocysts (92.6%) survived after warming and were transferred to 15 patients. five of the women became pregnant. conclusion: our results suggest that vitrified human day 5/day 6 blastocyst transfer which develop from poor quality embryo at day 3 can contribute to increasing cumulative pregnancy rates in assisted reproduction.