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Strategies to Detect Chromosomal Anomalies Not Identified by NIPT.
Fergus Scott1,2, May Phoo Han1, Ana Elizabeth Gomes de Melo Tavares Ferreira1,2
1Discipline of Women's Health, University of New South Wales, Randwick, Australia.
Prenatal Diagnosis
|February 21, 2025
Summary
Genome-wide non-invasive prenatal testing (gwNIPT) misses microdeletions and triploidy. Invasive testing, indicated by ultrasound findings or failed gwNIPT, detects most of these chromosomal abnormalities.
Area of Science:
- Prenatal diagnostics
- Genetics
- Maternal-fetal medicine
Background:
- Genome-wide non-invasive prenatal testing (gwNIPT) has limitations in detecting all chromosomal conditions, specifically microdeletions/microduplications (MD) and triploidy.
- Thickened nuchal translucency (NT) is a limited indicator for these conditions, identifying only about 10% of cases.
Purpose of the Study:
- To evaluate the detection rates of gwNIPT for chromosomal abnormalities.
- To identify factors leading to the detection of abnormalities missed by gwNIPT through invasive prenatal testing.
Main Methods:
- A 4-year retrospective study analyzed singleton pregnancies undergoing first-line gwNIPT followed by CVS or amniocentesis.
- Included analysis of all microdeletion/microduplication (MD) cases, regardless of prior gwNIPT screening.
Main Results:
- Of 919 pregnancies with gwNIPT and invasive testing, 338 had single chromosomal abnormalities. gwNIPT had 2.9% false negatives and missed 7.7% of abnormalities (18 MD, 8 triploidy).
- Approximately 90% of gwNIPT-missed anomalies were detected via invasive testing, prompted by failed NIPT (9%), low PAPP-A (12%), early growth restriction (37%), or structural anomalies (51%).
- Only 9% of missed cases presented with enlarged NT, and two of these also had structural abnormalities.
Conclusions:
- Most chromosomal abnormalities missed by gwNIPT are identified through invasive testing, often indicated by growth restriction or structural anomalies rather than enlarged NT.
- Failed gwNIPT and low PAPP-A levels were contributing factors in detecting missed chromosomal conditions.
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