The Relationship between Human Embryo Parameters and De Novo Chromosomal Abnormalities in Preimplantation Genetic Testing Cycles

Abstract

Research Question. What is the incidence of de novo chromosome abnormalities (>4 Mb), and are they related to embryo parameters in preimplantation genetic testing for chromosome structural rearrangement (PGT-SR) cycles and preimplantation genetic testing for aneuploidy (PGT-A) cycles? Design. In total, 456 PGT cycles, including 283 PGT-SR cycles and 173 PGT-A cycles, were assessed through comprehensive chromosome screening (CCS) from January 2017 to June 2020 at the Department of Reproductive Medicine of the Third Affiliated Hospital of Zhengzhou University. Trophectoderm (TE) biopsies were sequenced using next-generation sequencing (NGS). The incidence of de novo chromosome abnormalities was calculated, and the relationships between de novo chromosome abnormality rates and maternal age, number of oocytes retrieved, and parameters of cleavage-stage embryos and blastocyst-stage embryos were investigated. Results. The incidence of de novo chromosome abnormalities was 28.0% (318/1,135) in the PGT-SR cycles and 36.3% (214/590) in the PGT-A cycles, which increased with maternal age in both PGT-SR cycles ( P = 0.018) and PGT-A cycles ( P < 0.001). The incidence of de novo chromosome abnormalities was related to TE grade ( P < 0.001), internal cell mass grade ( P = 0.002), and development speed (day 5 vs. day 7: P < 0.001) of blastocyst-stage embryos. The incidence of de novo chromosomal abnormalities was irrelevant to the number of oocytes retrieved and the parameters of the embryo at the cleavage stage. Conclusion. Blastocysts with higher morphology scores and faster progression had a lower incidence of de novo chromosome abnormalities, especially complex chromosome abnormalities. De novo chromosome abnormalities may negatively affect the morphological grading of blastocysts. Our findings will provide valuable information to the fertility doctor for embryo selection in non-PGT cycles.

The correlation between morphological parameters and the incidence of de novo chromosomal abnormalities in 3238 biopsied blastocysts

“…The inconsistent results may be due to the different subjects and sample sizes included in the study. The average patient age in our study was younger than that of the abovementioned two studies[ 41 , 42 ]. The proportion of S-aneuploid blastocysts was lower (9.6%) than that of euploid (63.8%) and W-aneuploid (14.8%) blastocysts.…”

“…The average euploid blastocyst expansion rate is significantly faster than that of aneuploid blastocysts. Some studies suggest that a top-quality ICM and TE, higher expansion grade, and shorter time to the start of blastulation have a higher percentage of euploid blastocysts[ 30 , 39 ] and a lower incidence of de novo chromosomal abnormalities[ 41 ]. The conclusions about the relationship of morphological parameters with euploidy and aneuploidy are consistent with its effect on clinical outcomes, and our results are in accordance with these previous studies at the blastocyst chromosomal level.…”

“…A dataset from Escribà et al showed that there was no relationship between the incidence of segmental aneuploidy and the day of blastocyst biopsy or blastocyst stage, but the rate of segmental aneuploidy was significantly higher among blastocysts with poor ICM and TE quality[ 42 ]. Liu et al analyzed the incidence of de novo chromosome abnormalities related to embryo parameters in the cycles performed for chromosome structural rearrangement and PGT for aneuploidy[ 41 ]. The results showed that the incidence of de novo segmental chromosome abnormalities was significantly related to TE grade but not to ICM grade or blastocyst development speed.…”

Effects of chromosomal translocation characteristics on fertilization and blastocyst development — a retrospective cohort study

“…Research has indicated that individuals carrying chromosomal translocations exhibit a reduced rate of blastocyst formation and delayed blastocyst development. Various translocation characteristics, including carrier sex, translocation types and chromosome length, may exert distinct detrimental effects on the process of blastocyst development, as evidenced by relevant literature [ 7 – 9 ]. Scholars generally believe that the carrier sex and translocation type have significant effects on chromosome ploidy of blastocysts [ 10 – 12 ].…”