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Analysis of Embryos Using Next Generation Sequencing

Mosaicism, an early error in cell division that results in two or more cell lines with different genetic makeup, is common in the early stages of development. High-resolution next generation sequencing (hr-NGS) is a new, more sensitive way to detect mosaicism. Researchers are just beginning to unravel the ramifications of this condition, which can sometimes allow full-term pregnancies, or can lead to a higher risk of miscarriage and lower implantation rates.

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For purposes of the study, therefore, the researchers defined the conditions:

• Aneuploid: embryos with 1 or 2 aneuploid chromosomes or embryos with 1 aneuploid chromosome and 1 mosaic chromosome
• Complex abnormal: embryos with 3 aneuploid chromosomes or embryos with 2 aneuploid and 1 or more mosaic chromosomes
• Mosaic: embryos with a mixture of normal and abnormal cells

Rates of aneuploidy and complex abnormal embryos increased with age. Although mosaicism does not increase with age, in this study it actually decreased—likely due to classification of some mosaics as aneuploid.

The number of mosaic embryos in this study was significant, 11 to 23 percent, depending upon the age of the mother.

1. Munne et al. “PGS Analysis of Over 33,000 Blastocysts Using High Resolution Next Generation Sequencing (HRNGS).” Presented October 17, 2016, at ASRM 2016 Scientific Congress & Expo.

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