Description

The length of a fetus's ear may be an indicator of aneuploidy, especially when other sonographically detectable structural abnormalities are present.


 

Parameters:

(1) vertical length of the ear in mm

(2) gestational age in weeks

(3) 10th percentile for ear length for a gestational age and ethnic group (approximately 1.3 standard deviations below the mean)

(4) biparietal diameter in mm

 

biparietal diameter to ear length ratio =

= (biparietal diameter in mm) / (ear length in mm)

 

Criteria for aneuploidy:

(1) length of the ear <=10th percentile

(2) biparietal diameter to ear length ratio >= 4

 


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