Y. Shu

Live birth after transfer of a twice-vitrified warmed blastocyst that had undergone trophectoderm biopsy

A 28-year-old patient presented for preimplantation genetic screening (PGS) for family balancing utilizing previously vitrified blastocysts and day-2 embryos. To synchronize endometrial development with the embryos to be transferred, five embryos vitrified on day 2 were warmed 3 days prior to scheduled transfer. Three of them developed to 8-, 8- and 7-cell stages, respectively, and were biopsied the next day, during which three vitrified blastocysts were warmed and the two surviving blastocysts underwent trophectoderm biopsy. The five biopsied embryos were subjected to two-probe fluorescence in-situ hybridization for chromosomes X and Y. As there were still 2 days before the scheduled embryo transfer following biopsy, the two biopsied blastocysts were re-vitrified. One blastocyst and two of the embryos vitrified on day 2 were normal for sex chromosomes; of these, one of the day-2 vitrified embryos was arrested and the other did not favour the patients wish. The re-vitrified blastocyst, which was normal for sex chromosomes, was therefore warmed and transferred, resulting in delivery of one healthy boy. As far as is known, this is the first-reported live birth developed from a re-vitrified blastocyst that had been previously vitrified, warmed and undergone trophectoderm biopsy.