Chromosomal Anomalies in Fetuses With Increased Nuchal Translucency: A Vietnamese Retrospective Study

Area of Science:

• Prenatal genetics
• Fetal medicine
• Genomic diagnostics

Background:

• Increased nuchal translucency (NT) has historically been screened for aneuploidy.
• Recent studies highlight genetic disorders in euploid fetuses with thickened NT.
• Copy number variants (CNVs) are increasingly recognized in these cases.

Purpose of the Study:

• To determine the frequency of pathogenic CNVs (pCNVs) in euploid fetuses with increased NT.
• To identify factors associated with pCNVs in this population.
• To evaluate the utility of CMA and CNV-seq for prenatal diagnosis.

Main Methods:

• Retrospective study of 491 fetuses with NT ≥ 3 mm.
• Genetic testing performed using chorionic villus sampling or amniocentesis.
• Analysis by chromosomal microarray (CMA) or CNV-seq.

Main Results:

• Among 397 euploid fetuses, 9.1% had pCNVs.
• Submicroscopic pCNVs accounted for 6.0% of cases.
• The incidence of pCNV was higher in fetuses with additional structural abnormalities (OR 3.75).
• Maternal age and NT thickness were not significantly associated with pCNV risk.

Conclusions:

• CMA and CNV-seq effectively detect pCNVs in euploid fetuses with increased NT.
• These genetic tests provide valuable information for prenatal counseling.
• Identifying pCNVs improves diagnostic yield beyond aneuploidy screening.