Clinical success with vitrification following trophectoderm biopsy for comprehensive chromosomal screening

Abstract

OBJECTIVE: Trophectoderm (TE) biopsy can be performed on either D5 or D6 post oocyte retrieval relative to blastocyst development. Accordingly, cryopreservation becomes an essential clinical component as limited time is available for genetic analysis prior to the timing for a fresh transfer. The aim of this study was to evaluate the efficacy of vitrification following TE biopsy of human blastocysts for comprehensive chromosomal screening (CCS) . DESIGN: Prospective study. MATERIALS AND METHODS: Seventy patients (mean 37.4yrs) were recruited for TE biopsy followed by vitrification with a subsequent frozen blastocyst transfer (FBT). A hole in the zona pellucida was created on D3 of culture. At the blastocyst stage, TE cells protruding out of the breach were biopsied for genetic analysis. CCS was performed by comparative genomic hybridization (Reprogenetics) or single nucleotide polymorphism microarray (RMA-NJ). Biopsied blastocysts were subsequently vitrified utilizing the cryotop device with a DMSO/ethylene glycol protocol. RESULTS: The survival rate following vitrification and warming of biopsied blastocysts was 99.3% (142/143). Seventy patients have received a transfer of chromosomally euploid blastocysts in an FBT cycle (mean transferred = 1.99). Clinical pregnancy with positive fetal heart tones (FHT) was detected in 57 of the 70 patients (81.4%) with 87 positive FHT implantations (62.6%) from 139 blastocysts transferred. During the same time period, 272 patients underwent an FBT with non-biopsied conventionally frozen blastocysts. Survival rate after thawing was 83% (681/820) (P<0.0001), with a 57% (156/272) clinical pregnancy rate (FHT) (P<0.001) and 35% (211/600) implantation rate (FHT) (P<0.0001). CONCLUSIONS: High survival, pregnancy and implantation rates were observed following blastocyst biopsy, CCS and vitrification. Vitrification is a successful means for cryopreservation of human biopsied blastocysts and allows for time interval required for genetic analysis of D5 and D6 human blastocysts in an IVF cycle.