Genetics and screening for foetal abnormality

Question 1

What are the RFs for a woman having a high risk pregnancy?

Answer 1

1. Maternal age >35y/o
2. Previous abnormal baby
3. FHx of inherited condition

Question 2

What is also looked for in the gestational scan?

Answer 2

1. Viability
2. Gestational age
3. Chorionicity
4. FNT
5. Malformation

Question 3

What is FNT a measure of?

Answer 3

Fluid accumulation in the neck

Question 4

What is the PPV of FNT?

Answer 4

Only 4% - therefore 96% who undergo FNT actually don’t have a chromosomal abnormality

Question 5

What is AFP?

Answer 5

Alpha-fetoprotein

Question 6

Where is AFP produced?

Answer 6

Foetal liver and GI tract

Question 7

What may high levels of AFP indicate?

Answer 7

1. Open neural tube defect
2. Exomphalos
3. Posterior urethral valves
4. Nephrosis
5. GI obstruction
6. Teratoma
7. Turner’s syndrome

Question 8

What are the elements of the combined test for screening for Down’s syndrome?

Answer 8

FNP + PAPP-A + beta-hCG

Question 9

Why may FNP not be able to be measured?

Answer 9

1. Maternal obesity

2. Foetus lie

Question 10

What should be offered if FNP can’t be measured?

Answer 10

The triple or quadruple test

Question 11

What are the elements of the triple test?

Answer 11

AFP + estriol + beta-hCG

Question 12

What are the elements of the quadruple test?

Answer 12

AFP + estriol + beta-hCG + inhibin A

Question 13

Following the anomaly scan - what should prompt a referral to a foetal medicine specialist?

Answer 13

1. Nuchal fold >/=6mm

2. >=2 soft markers - 1) increased nuchal thickness; 2) choroid plexus cysts; 3) echogenic bowel

Question 14

What is CVS?

Answer 14

A placental biopsy

Question 15

When should CVS be performed?

Answer 15

Not before 10 weeks, and not after 20 weeks

Question 16

What is the foetal loss rate?

Answer 16

4/100

Question 17

What are the problems with CVS?

Answer 17

1. Does not detect NTDs

2. May cause foetal malformation

Question 18

When should amniocentesis be performed and why?

Answer 18

After 15 weeks, because before then there is an increased rate of foetal loss, an increased incidence of foetal talipes and respiratory morbidity

Question 19

What is the foetal loss rate in amniocentesis?

Answer 19

1/100 at 16 weeks

Question 20

What defines recurrent spontaneous miscarriage (RSM)?

Answer 20

> /=3 miscarriages that occur in succession

Question 21

What is a late miscarriage?

Answer 21

14-24 weeks

Question 22

When is it defined as a stillbirth?

Answer 22

> 24 weeks

Question 23

What are the possible causes of RSM?

Answer 23

1. Chromosomal translocation
2. Anti-phospholipid syndrome
3. Infection - BV can cause late RSM
4. Thromophilia
5. Endocrine - e.g. PCOS
6. Anatomical abnormality - e.g. cervical incompetence or uterine abnormality

Question 24

What are the 3 main types of abnormal morphogenesis?

Answer 24

1. Deformation
2. Malformation
3. Disruption

Question 25

What are malformations caused by?

Answer 25

An intrinsic problems within the developing structure

Question 26

What is a deformation caused by?

Answer 26

An extrinsic force on a normally developing or developed structure - usually occur late in foetal life caused by a lack of foetal movement through one of either 1) mechanical factors; 2) malformation factors; 3) functional factors

Question 27

What is a disruption caused by?

Answer 27

A destructive force acting upon an otherwise normal developing structure

Question 28

What is the VATER association?

Answer 28

V - vertebral anomalies
A - anal atresia
T - tracheo-
E - esophageal fistula
R - radial and renal anomalies