Growing zona pellucida-free (ZPF) oocytes from ICSI to biopsy: it works

Abstract

day 5, 6, and 7 blastocysts in order to determine the efficacy of extended D7 culture in our laboratory. Materials and Methods: Over the span of 3 years, a total of 1915 blastocyst stage embryos (average maternal age of 37 ± 4.1 years) underwent trophectoderm biopsy for genetic testing of ploidy status. Pre-implantation genetic screening (PGS) results were retrospectively compared to day of trophectoderm biopsy. Mature oocytes were fertilized using ICSI and embryos were group cultured in a continuous single culture medium (Irvine Scientific). On Day 3 of embryo development, all multi-cell embryos (≥6 cells) were artificially hatched by laser ablation of the zona pellucida. Hatched embryos were then cultured to the blastocyst stage. Trophectoderm biopsy was dependent on development of a well-defined inner cell mass and trophectoderm. Hatching or completely hatched blastocysts were biopsied on either Day 5, 6 or 7 and subsequently vitrified for future use in a warmed embryo transfer cycle dependent on ploidy status. Biopsied samples were analyzed with comprehensive chromosomal screening involving the use of array comparative genomic hybridization (aCGH) or next generation sequencing (NGS) technology by a reference laboratory. Results: 1915 embryos were biopsied yielding a total of 862 (45%) euploid embryos: 485(56%), 328(38%) and 49(5.7%) from D5, D6, and D7, respectively. The incidence of euploidy was 50%, 40%, and 38% among D5, D6, and D7. Chi-square analysis demonstrated that euploid status is dependent on day of biopsy/blastocyst development with chi square statistic calculated to be 17.5847 and a P value < 0.0001 (Figure 1).