P–148 Effect of additional laser assisted drilling (LAD) during trophectoderm (TE) biopsy on mosaicism rate

Abstract

Abstract Study question Does applying additional LAD during TE biopsy cause higher mosaicism rate in blastocysts? Summary answer Applying LAD during TE biopsy to create additional zona opening will produce more mosaic blastocysts. What is known already In Alpha IVF, laser assisted hatching (LAH) was done on day3 after ICSI for all pre-implantation genetic testing for aneuploidy (PGT-A) cycles. TE biopsy techniques used were laser+pulling (L+P), laser+flicking (L+F) and flicking only (F). At the time of biopsy, an extra step of creating additinonal artificial opening by LAD may be required when (a) blastocyst has very little herniated cells; (b) inner cell mass (ICM) is at the hatching point or biopsy site. Our internal study showed that biopsy using different techniques (L+P, L+F and F) does not affect mosaicism rate. Study design, size, duration This prospective study was designed to evaluate the effect of additional LAD during TE biopsy on the mosaicism rate. This study was conducted between 11th March–19th August 2019. Four hundred forty-three (443) patients had undergone oocyte retrieval and blastocyst culture after intracytoplasmic injection (ICSI) was done. A total of 824 hatching blastocyst (BG5) and fully hatched blastocyst (BG6) with at least a Grade A or Grade B TE (Gardner’s grading) were included in this study. Participants/materials, setting, methods LAH was done on day3 post-ICSI while biopsy was done on day5 and/or day6 for PGT-A. Laser pulse length used during LAH and biopsy was fixed at 400ms. The biopsied blastocysts were classified into 3 groups: (A) BG6 (n = 79), (B) BG5 without additional LAD during biopsy (n = 713) and (C) BG5 with additional LAD (n = 32). The number of biopsied cells ranged from 5–10 cells. Biopsied cells were tested using Next Generation Sequencing (Ion Torrent, USA). Main results and the role of chance The mosaicism rates for Group A, B and C were 19.0% (15/79), 23.4% (167/713) and 39.5% (15/38) respectively. Mosaicism rates of Group A and B were comparable (p = 0.4807), whilst Group C had significant higher mosaicism rate compared to Group A and B (p = 0.0238 and p = 0.0319 respectively). The mean age of Group A, B and C were 31.1, 31.4 and 27.1 respectively. The mean age between these 3 groups were not statistically significant (A vs B, p = 0.0713; A vs C, p = 0.06727; and B vs C, p = 0.4408). Limitations, reasons for caution Additional LAD during TE biopsy maybe be a confounding variable which affects the mosaicism rate. Moreover, the increase in mosaicism rate could be due to other unknown factors. A larger sample size is needed to confirm the results. Wider implications of the findings: Based on our study, additional LAD during TE biopsy is not recommended as this may increase mosaicism rate. Biopsy should be done when the blastocyst has more herniated cell or when the ICM leaves the hatching point/biopsy site. Trial registration number Not applicable