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Absent nasal bone

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

Radiographic assessment

Antenatal ultrasound

It is assessed on a midline sagittal view. There 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 coronal view of the fetal face to look for paired echogenic structures located at the upper tip of the retronasal triangle 6


The incidence of an absent nasal bone is related to NT, 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

See also

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