Increased nuchal translucency thickness and normal chromosomal microarray: Danish nationwide cohort study

Area of Science:

• Prenatal diagnostics
• Genetics
• Obstetrics

Background:

• Increased fetal nuchal translucency (NT) thickness is a marker for chromosomal abnormalities.
• Chromosomal microarray (CMA) offers higher resolution than conventional karyotyping for detecting genetic aberrations.

Purpose of the Study:

• To compare pregnancy outcomes in cases of increased NT with normal chromosomal microarray (CMA) versus conventional karyotyping.
• To assess the diagnostic yield and prognostic value of CMA in pregnancies with increased NT.

Main Methods:

• Nationwide Danish registry-based cohort study (2008-2018) of singleton pregnancies.
• Stratification by NT thickness and comparison of outcomes between CMA and conventional karyotyping.
• Analysis included chromosomal aberrations, termination, pregnancy loss, malformations, and unaffected live births.

Main Results:

• Prevalence of chromosomal aberrations increased with NT thickness (21% for 3.5-4.4mm to 69% for ≥6.5mm).
• In pregnancies with increased NT and normal CMA, unaffected live birth rates decreased significantly with increasing NT (87% to 29%).
• Normal CMA results did not substantially improve prognosis compared to normal conventional karyotyping for increased NT.

Conclusions:

• Confirms the association between increased NT and chromosomal aberrations.
• Despite improved diagnostic resolution with CMA, normal results do not significantly change the prevalence of unaffected live births.
• Highlights the need for ongoing research and accurate clinical guidance in prenatal care.