**1. Introduction**

Embryonic aneuploidy in human in vitro fertilization (IVF) is very common and is one of the factors reducing embryo implantation and causing birth defects. Although aneuploidy is mainly observed in the embryos from patients with advanced maternal ages [1–3], it is also very common in the embryos from young patients and oocyte donors [4–9]. The frequencies of aneuploid embryos produced by IVF have been widely studied [4–12] by examination of all chromosomes with microarray and next generation of sequencing (NGS) through preimplantation genetic testing for

aneuploidies (PGT-A) [13–17]. With PGT-A by NGS, not only a whole chromosome aneuploidy can be detected, but also segmental chromosome abnormalities (deletion and duplication) can be detected [18–21]. Segmental chromosome abnormalities typically represent regional losses or gains in one or more chromosomes. The size of a segmental abnormalities detectable by current NGS platforms is as small as 1 Mb, however, for PGT-A, usually 10 Mb and above are detected and reported.

Some segmental chromosome abnormalities may cause miscarriage and birth defect, while others may result in developmental delay and/or intellectual disability if the transfer of such embryos produce live birth. It has been found that the prevalence of embryonic aneuploidy in donor egg IVF was significantly different between fertility clinics indicating that clinical and laboratory procedures may be related to the occurrence of embryonic aneuploidies [12]. Embryo biopsy is a complicated and invasive laboratory procedure that involves several embryo manipulations during culture, so it may affect embryo's quality including aneuploidies. Therefore, in the present study, to examine whether embryo biopsy procedures affect embryonic aneuploidies in donor egg IVF, blastocysts were biopsied by two different biopsy methods and then the samples were examined by NGS. Collected data were analyzed in terms of the rates of embryos with whole chromosome aneuploidies and segmental chromosome abnormalities. Clinical outcomes, such as pregnant rate, live birth rate and embryo implantation rate were also analyzed.
