THE GENETIC SONOGRAM  


Genetic Sonogram Template

 

Ultrasound cannot be used to diagnose or exclude chromosomal aneuploidy or Down syndrome:

 

 

Down Syndrome:

  1. Structural abnormalities that have clinical consequences despite the abnormal karyotype:

 

  1. Markers or traits that have no serious structural consequence except their relationship to aneuploidy:

·        Although each marker has a sensitivity for Down syndrome, most are found frequently as an isolated finding in normal fetuses.

·        Many are transient and resolve in the third trimester.

·        What are their roles in the low risk patient????? controversial.

·        In high-risk patients, they form the basis for the genetic sonogram as they can increase the risk or likelihood ratio if a marker is present, but can also lower the risk in their absence.

 

Marker

All Cases

Isolated Marker

DS (%)

Control (%)

LR (%)

DS (%)

Control (%)

LR (%)

Nuchal fold – 6mm or greater

42.3

0.5

94.7

(30.2-296.7)

3.7

0

NC

Nuchal fold –       5 mm or greater

47

0.8

61.6

(25.3-149.7)

ND

ND

ND

Short humerus

48.7

2.1

23.5

(13.1 – 42.1)

2

0.4

5.8

Short femur

53.7

5.3

10.1

(7.1 – 14.3)

4.3

3.7

1.2

(0.51 – 2.7)

Hyperechogenic bowel

13

0.9

14.4

(5.4 – 38.1)

0

0.7

NC

EIF

34.2

4.3

8

(4.8-13.3)

5.4

3.8

1.4

(0.6 – 4.3)

Pyelectasis

21.3

2.4

8.8

(5.0 – 15.4)

3.1

2.0

1.5

(0.6 – 4.3)

Anomaly

26.8

1.2

22

(10.6 – 45.8)

3.1

0.9

3.3

(1.0 – 10.8)

Any marker

80.5

12.4

6.5

(5.3 – 8.1)

ND

ND

ND

No abnormality

19.5

87.7

0.22

(0.16 – 0.3)

ND

ND

ND

 

 

 

 


Explanation of likelihood ratio (LR) values


 

 

 


Priori risk of carrying a fetus with DS (based on maternal risk and serum screening)

X

LR of the presence of a sonographic finding

=

New risk estimate for having a fetus with DS

Patients Age

(yrs)

Risk of DS based

on maternal age

Pyelectasis

EIF

Echogenic bowel

Humerus

Nuchal

Thickening

LR

 

LR = 1.5

LR = 2

LR = 6.1

LR = 5.2

LR = 15.5

20

1/1521

1/1014

1/760

1/250

1/295

1/98

30

1/910

1/606

1/380

 

 

1/58

35

1/385

1/256

1/178

 

 

1/24

40

1/113

1/75

1/57

 

 

1/7.2

 

 

Relationship between maternal age and the presence of ultrasound markers


Relationship between Maternal serum screening and ultrasound markers of chromosomal aneuploidy


 

 

 

 

 

 


REFERENCES