P–557 Trophectoderm biopsy technique and rate of mosaicism in human blastocysts

Study question Do different trophectoderm biopsy techniques affect mosaicism rate in human blastocysts? Summary answer No statistical significance was found between biopsy techniques and mosaicism rate. However, an increase in mosaicism rate was observed when the flicking technique was used. What is known already Mosaicism is defined as two or more distinct cell lines within an embryo. Recent advances in Next Generation Sequencing (NGS) technology with an increased sensitivity allows a higher accuracy in quantification of mosaic levels in biopsied cells. The incidence of mosaicism is widely debated as there are many attributing technical and biological factors. Since, trophectoderm biopsy is a technically challenging process, it is crucial to ensure that the both biopsied cells and blastocyst suffers minimal damage during biopsy. Study design, size, duration This is a prospective study involving 222 patients (age range= 18–44, mean age= 31.5) who underwent IVF cycles in Alpha IVF, Malaysia from March 2019 to August 2019. Six hundred and sixty-eight (668) of the blastocysts were biopsied on Day 5 (Group 1) while 177 blastocysts were biopsied on Day 6 (Group 2). The blastocysts in these groups were further categorised into their corresponding biopsy techniques: (A) laser+pulling; (B) laser+flicking; (C) flicking only. Participants/materials, setting, methods Blastocysts which were at least fair graded (Gardner, 1999) were biopsied and vitrified (Cryotec, Japan). The number of biopsied cells ranged from 5 to 10 cells. All biopsied trophectoderm samples were subjected to Preimplantation Genetic Testing for Aneuploidy (PGT-A) with Next Generation Sequencing (NGS) (Ion Torrent, USA). Chromosomal mosaicism analysis was done using ReproSeq Mosaic PGS w1.1 workflow. Trophectoderm biopsied sample which were tested to have 20% to 80% aneuploid cells were reported as mosaic. Main results and the role of chance In Group 1, the mosaicism rates for biopsy technique A, B and C were 23.3% (104/446), 28.2% (58/206) and 37.5% (6/16) respectively. In Group 2, the mosaicism rates for biopsy technique A, B and C were 14.6% (7/48), 19.5% (23/118) and 27.3% (3/11) respectively. There were no significant differences (p > 0.05) in mosaicism rates between all study groups and subgroups. Limitations, reasons for caution Although no statistical significance was found between trophectoderm biopsy techniques and the prevalence of mosaicism, there is a trend of an increase in mosaicism rate when the flicking technique was used. Therefore, further studies with a larger sample size should be undertaken. Wider implications of the findings: Our study demonstrates a trend in the decrease of mosaicism rate when laser pulses was used to loosen the cell junction of targeted cells. Hence, in place of the flicking method alone, laser pulses should be applied during trophectoderm biopsy if our findings are confirmed in a larger controlled study. Trial registration number Not applicable