Cut-off value of nuchal translucency as indication for chromosomal microarray analysis.

Area of Science:

• Prenatal diagnosis
• Fetal medicine
• Genetics

Background:

• Increased nuchal translucency (NT) is associated with chromosomal abnormalities.
• Current NT cut-off values for genetic testing may not be optimal.
• Revisiting NT cut-off levels is crucial for accurate risk assessment.

Purpose of the Study:

• To evaluate different NT cut-off levels for recommending chromosomal microarray analysis (CMA).
• To determine if CMA is indicated for mildly increased NT (3.0-3.4 mm).

Main Methods:

• Retrospective, multicenter study of singleton pregnancies with CMA results.
• Categorization of NT measurements into three groups: ≤ 2.9 mm, 3.0-3.4 mm, and ≥ 3.5 mm.
• Comparison of CMA results across NT groups for isolated findings.

Main Results:

• Pathogenic copy number variants were identified in 1.7% of fetuses with NT ≤ 2.9 mm.
• A significant increase to 6.5% for fetuses with NT 3.0-3.4 mm.
• 13.8% of fetuses with NT ≥ 3.5 mm showed pathogenic variants.

Conclusions:

• CMA should be recommended for isolated, mildly increased NT (3.0-3.4 mm).
• This finding supports expanding CMA indications in prenatal screening.
• Optimizing NT cut-offs improves detection of fetal genetic abnormalities.