AB095. Comparison pregnancy of day 6 fresh blastocyst and day 5 frozen-thawed blastocyst transfer following array comparative genome hybridization (aCGH)

Abstract: Advances in assisted reproductive technologies (ART) have benefitted many infertile couples. However while many modern technologies were applied in ART, pregnancy rates remained lower than expected. Some studies have suggested that successful embryo implantation depends on many factors including genetic anomalies such as aneuploidy. While pre-implantation genetic screening (PGS) using fluorescent in situ hybridization (FISH) was introduced around 20 years ago to screen for aneuploidy in selected subsets of chromosomes, it failed to improve pregnancy rates and reduce miscarriage rates. FISH had technical limitations, some inaccuracies, and could only screen up to 8-11 chromosomes. Recent more modern technology, array comparative genome hybridization (aCGH), has been shown to significantly improve pregnancy rates and decrease miscarriage rates by allowing the detection of aneuploidy in all 23 pairs of chromosomes, and allowing the transfer of euploid embryos. Couples have an ovarian stimulation, eggs are collected and fertilized using intracytoplasmic sperm injection (ICSI), and any normally fertilized embryos are cultured to the blastocyst stage. Suitable blastocysts are biopsied on either day 5 or day 6 of embryo culture with the assistance of a near-infra-red laser, and the removed cells amplified in a whole genome amplification (WGA), fluorescently labelled, hybridized and scanned using the BlueGnome (Illumina) 24Sure CGH microarray system. Advances in aCGH means the total process from biopsy to result can be done overnight, allowing for a suitable embryo from a day 5 biopsy to have potential fresh embryo transfer on day 6 of culture. Alternatively, following biopsy, embryos can be frozen immediately and euploid embryos transferred in a subsequent frozen-thaw cycle. We retrospectively compared pregnancy outcomes of good quality blastocysts biopsied and analysed using aCGH following by fresh embryo transfer on day 6 (n=50) versus frozen embryo transfer of embryos biopsied and frozen on day 5 (n=61). The average age of patients having a fresh embryo transfer on day 6 is 32±3.2 and having frozen embryo transfer is 30±3.7 years old. The results showed that pregnancy rates were not significantly different between frozen embryo transfer and fresh embryo transfer (59% vs. 52% respectively, P value >0.05). Nevertheless, as well as indicating that not only is frozen embryo transfer as good as or better than fresh embryo transfer, frozen embryo transfer can also have advantages in in-vitro fertilization in allowing optimal embryo transfer planning for couples.

Keywords: Array comparative genome hybridization (aCGH); in vitro fertilization, fresh blastocyst transfer; frozen-thawed blastocyst transfer