Copy Number Variant Detection by NIPT: Biological Constraints and the Limits of Prenatal Genomic Inference

Area of Science:

• Genomics
• Prenatal Diagnostics
• Bioinformatics

Background:

• Non-invasive prenatal testing (NIPT) using cell-free fetal DNA (cfDNA) has advanced aneuploidy screening.
• NIPT is expanding to detect genome-wide copy number variants (CNVs).
• Current CNV detection by NIPT is limited by analytical and biological complexities.

Purpose of the Study:

• To review the analytical validity of NIPT for CNV detection.
• To evaluate biological constraints and interpretation challenges in NIPT-based CNV analysis.
• To frame NIPT CNV detection as probabilistic genomic inference.

Main Methods:

• Review of analytical validity and biological constraints of NIPT for CNVs.
• Evaluation of factors influencing CNV detection performance (sequencing depth, fetal fraction, etc.).
• Analysis of biological sources of discordance (placental mosaicism, maternal factors).

Main Results:

• NIPT CNV detection performance varies based on technical and biological factors.
• Confined placental mosaicism, maternal CNVs, and other events complicate interpretation.
• Clinical validity is heterogeneous, with inconsistent reporting practices.

Conclusions:

• NIPT CNV detection is limited by the composite maternal-placental cfDNA signal.
• Advancements necessitate improved tissue-of-origin discrimination.
• Multi-omic integration and standardized reporting are crucial for responsible clinical implementation.