The Impact of Nasal Bone Reporting on Down Syndrome Prognosis: A Prospective Study

Maryam  Rahnama; Atefeh  Manzoury; Atefeh  Manzoury; Neda  Rashidmehr; Navid  Ghasemzadeh; Majid  Mojarrad

doi:10.18502/abi.v3i3.20592

Maryam Rahnama Genetic Foundation of Khorasan Razavi, Mashhad, Iran.
Atefeh Manzoury Genetic Foundation of Khorasan Razavi, Mashhad, Iran.
Atefeh Manzoury Genetic Foundation of Khorasan Razavi, Mashhad, Iran.
Neda Rashidmehr Genetic Foundation of Khorasan Razavi, Mashhad, Iran.
Navid Ghasemzadeh Department of Clinical Biochemistry, Faculty of Medicine, Urmia University of Medical Sciences, Urmia, Iran.
Majid Mojarrad Genetic Foundation of Khorasan Razavi, Mashhad, Iran.

DOI: https://doi.org/10.18502/abi.v3i3.20592

Keywords: Contingent prenatal screening test, Down syndrome, Nasal bone, Trisomy 21

Abstract

Objectives: Accurate prenatal screening for Down syndrome (trisomy 21) is essential for effective maternal-fetal management. The nasal bone (NB) is a critical marker in first-trimester ultrasound assessments, yet reporting inconsistencies can affect prognostic outcomes. This study aims to investigate the impact of reporting the presence or absence of the nasal bone on Down syndrome prognosis in a cohort of pregnant women.

Methods: A prospective study was conducted involving women undergoing contingent prenatal screening during the first trimester. Participants with documented present NB were classified as having unknown NB, while those with unknown reports were treated as having present NB. The risk of Down syndrome was assessed using Benetech-PRA software, and all flagged cases were monitored postpartum to evaluate outcomes.

Results: Of the fetuses assessed, only 5% were diagnosed with Down syndrome. Approximately 7.3% of sonographers reported unknown NB, which was associated with a false-positive screening rate of 16±1%. The findings indicate that NB reporting significantly influences prognostic outcomes, particularly in cases where the NB status is unclear.

Conclusion: Accurate examination and reporting of the nasal bone are critical for reliable Down syndrome prognosis. Inadequate or incorrect NB assessment can lead to misleading results and increased false-positive rates in prenatal screening, underscoring the need for standardized reporting practices in ultrasound examinations.