P-160 Trophectoderm biopsy techniques with and without laser use and their contribution to PGT-A results in sibling embryos
Authors: Coban O , Yarkiner Z , Çal T , Soykök A , Bankeroglu H 
Published: June 2023

Abstract

Study question
Do the methods used in trophectoderm biopsy and the use of laser affect the genetic results of the harvested cells and the embryos thus examined?

Summary answer
The different methods of trophectoderm biopsy showed no differences in terms of euploidy rate and the specific type of chromosomal abnormalities.

What is known already
Next generation sequencing (NGS) is a comprehensive method for the genetic screening of preimplantation embryos and is now favored by many clinics. The method can detect structural abnormalities on all chromosomes and offers better reproductive success compared to earlier tests. However, as the test is very sensitive, biopsy of the embryo and treatment of the biopsied embryos and harvested cells are important to improve diagnostic success. Contamination of the biopsied sample can affect the results of the genetic test and lead to misdiagnosis.

Study design, size, duration
A prospective, randomized controlled trial of 44 couples undergoing infertility treatment with pre-implantation genetic screening (PGT-A, NGS) at the British Cyprus IVF Hospital between October 2021 and December 2022.

Participants/materials, setting, methods
PGT-A cases with more than two blastocysts were included in the study. Randomization was performed on days 5 and 6 of embryo development and embryos were divided into two groups before the biopsy. In group 1, embryos were biopsied using the flicking method without laser assistance. In group 2 embryos, cells were removed by pulling the desired cells with 3 to 5 laser shots at the edge of the selected cell group.

Main results and the role of chance
PGT-A results of 288 blastocyst-stage embryos from 44 cases were analyzed. 136 embryos were in group 1 (flicking) and 152 to group 2 (laser). The embryos in the groups were siblings, so the basic patient characteristics, number of eggs retrieved, sperm characteristics, and early embryonic details were identical between the groups. The mean number of retrieved cells was 6.19 ± 0.915 and 6.14 ± 0.849 (p = 0.764), the number of euploid embryos was 49/122 (40.2%) and 57/137 (41.6%) (p = 0.814), the number of embryos with whole chromosome aneuploidy was 46/73 (63%) and 58/80 (72.5%) (p = 0.209) and embryos with complex aneuploidy (more than two abnormal chromosomes) were 30/73 (41.1%) and 40/80 (50%) (p = 0.268) in group 1 and group 2, respectively.

Limitations, reasons for caution
As this is a preliminary research result, the small sample size is the major limitation. Mosaicism, which is common in preimplantation embryos and has a significant impact on the results, was not investigated.

Wider implications of the findings
Although the present data showed no differences between the two biopsy procedures in terms of PGT-A test results, invasive embryo biopsy procedures can damage embryos or misdirect genetic test results. Therefore, validation and universalization of the method for embryo biopsy are needed, which is emerging in recent publications.

Trial registration number
not applicable