Chromosome constitution of equal-sized three-cell embryos using next-generation sequencing technology

Area of Science:

• Reproductive biology
• Genetics
• Embryology

Background:

• Chromosomal abnormalities in early embryos can impact implantation and development.
• Accurate assessment of embryonic aneuploidy is crucial for successful in vitro fertilization (IVF).

Purpose of the Study:

• To investigate the chromosomal constitution of equal-sized three-cell embryos.
• To determine if blastomere morphology correlates with chromosomal normality.

Main Methods:

• Utilized multiple annealing and looping-based amplification cycles (MALBAC) and next-generation sequencing (NGS) to analyze chromosomal copy number variation (CNV).
• Assessed blastomere morphology, including radius, perimeter, area, and volume, in 35 embryos.
• Performed CNV analysis on 105 blastomeres from 27 embryos.

Main Results:

• A significant majority (77.8%) of the analyzed embryos were mosaic or aneuploid.
• Aneuploidies were widespread, with chromosomes 1, 16, and 18 being the most frequently affected.
• No significant morphological differences were observed between euploid and aneuploid embryos.

Conclusions:

• Most equal-sized three-cell embryos exhibit chromosomal abnormalities.
• Embryonic morphology is not a reliable indicator of chromosomal normality in these embryos.
• Equal-sized three-cell embryos with abnormal chromosome numbers should be considered for lower priority during embryo selection for transfer.