Absent nasal bone

In a fetal sonographic assessment, an absent nasal bone is a feature which can sometimes be used as an adjunctive marker for fetal aneuploidy.

It is assessed on a midline sagittal view. In this section, the nasal bone is often seen as a bright echogenic line. It is best visualised at around 11th to 14th weeks of gestation (1st trimester). A magnified image may assist in visualisation.

When the mid sagittal view is difficult to assess, some authors suggest a coronal view of the fetal face to look for paired echogenic structures located at the upper tip of the retronasal triangle 6

When the nasal bone is absent at 11 to 12 weeks, while the other ultrasound markers and serum biochemistry are normal; a follow up scan after a week is suggested.

The incidence of an absent nasal bone is related to nuchal translucency (NT), crown rump length (CRL), and ethnic origin, as well as aneuploidy. It is more common with increased NT, smaller CRL measurements and in fetuses of Afro-Caribbean parents. 

The reported prevalence range of an absent nasal bone on ultrasound for euploid as well as the following aneuploidic states are

Ultrasound - obstetric
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Article information

rID: 12804
System: Obstetrics
Section: Signs
Tag: cases
Synonyms or Alternate Spellings:
  • Absence of nasal bone
  • Nasal bone absence
  • Nasal bone absent

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Cases and figures

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    Case 1: absent nasal bone
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