Clinical utility and limitations of non‐invasive prenatal testing for chromosome 20 abnormalities: A retrospective study of 83 high‐risk pregnancies

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OBJECTIVE: To evaluate the performance of non-invasive prenatal testing (NIPT) in detecting chromosome 20 abnormalities and to investigate the associated pregnancy outcomes. METHODS: This retrospective cohort study included 83 singleton pregnancies referred for invasive prenatal diagnosis following high-risk NIPT results for chromosome 20 abnormalities between January 2019 and February 2024. Clinical data were obtained from medical records and telephone interviews. RESULTS: NIPT identified 67 cases of aneuploidies (including 63 cases of trisomy 20 and 4 cases of monosomy 20) and 16 cases of clinically significant copy number variations (CNVs). Following invasive prenatal diagnosis, nine cases were identified with positive chromosomal microarray analysis or karyotyping results. Among these, only four NIPT results were confirmed as true positives, yielding an overall positive predictive value (PPV) of 4.8% (4/83). The PPV for CNVs (18.8%, 3/16) was significantly higher than that for aneuploidies (1.5%, 1/67; P = 0.021). Of the 79 pregnancies with available follow-up data, 71 (89.9%) resulted in live births. Two children with normal prenatal diagnostic results exhibited short stature and a language disorder, respectively, while the remaining children had favorable outcomes. CONCLUSION: NIPT demonstrates very limited accuracy for detecting chromosome 20 aneuploidies, while its performance in identifying CNVs is comparatively higher but remains modest. The favorable outcomes in most cases with normal diagnostic results underscore the importance of cautious reporting and interpretation of high-risk results for chromosome 20 abnormalities as well as comprehensive genetic counseling to guide pregnancy management.

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