First-trimester nasal bone evaluation for aneuploidy in the general population

Area of Science:

• Prenatal diagnostics
• Fetal medicine
• Genetics

Background:

• Aneuploidy screening in early pregnancy is crucial for identifying chromosomal abnormalities.
• Nuchal translucency (NT) ultrasound is a standard first-trimester screening method.
• The potential role of other fetal markers, like nasal bone ossification, is under investigation.

Purpose of the Study:

• To assess the efficacy of fetal nasal bone imaging as a screening tool for aneuploidy.
• To evaluate its contribution when combined with nuchal translucency (NT) screening.
• To determine its utility in a large, unselected population during the first trimester.

Main Methods:

• A prospective multicenter trial involving 38,189 pregnancies.
• Nuchal translucency (NT) ultrasound screening was performed on all participants.
• First-trimester nasal bone evaluation was added to the protocol for a subset of 6,324 patients.
• Nasal bone status was categorized as present, absent, or unable to determine.

Main Results:

• Nasal bone images were obtained in 76% of cases where attempted.
• Nasal bones were present in 99.5% of evaluable cases.
• Absence of nasal bones showed a sensitivity of 7.7% for aneuploidy.
• The positive predictive value for absent nasal bones was 4.5%.

Conclusions:

• First-trimester nasal bone evaluation is not a valuable screening test for trisomy-21 in the general population.
• It offers minimal added benefit to first-trimester NT screening.
• Consistent performance of first-trimester nasal bone sonography is challenging, limiting its clinical utility for aneuploidy screening.