Genetics 31 - 33

Question 1

Four screening tests for fetal aneuploidy?

Answer 1

1. NT screen
2. Quad screen
3. Non-invasive prenatal screening (cfDNA) - NIPS
4. Ultrasound

Question 2

Three diagnostic tests for fetal aneuploidy?

Answer 2

1. CVS
2. amniocentesis
3. Fetal umbilical blood sampling (cordocentesis)

Question 3

Karyotype abnormality most likely to be associated with cystic hygroma?

Answer 3

45,X - Turner Syndrome

Question 4

Ultrasound “marker” most likely to be associated with a fetus with trisomy 21?

Answer 4

Thickened nuchal fold

Question 5

Karyotype abnormality most likely to be associated with the ultrasound finding of “double bubble”

Answer 5

Trisomy 21

Question 6

Best non-invasive test for fetal aneuploidy in a patient at 12 weeks gestation?

Answer 6

NIPS (cfDNA)

Question 7

Clinical features of Edwards Syndrome?

Answer 7

overlapping fingers, rocker bottom feet, short sternum, excessive hair growth (hirsutism), cardiac anomalies, profound delays, prenatal growth deficiency, small mouth, low-set ears, small jaw

Question 8

Genetic cause of Trisomy 18?

Answer 8

90-95% is maternal nondisjunction (50% of meiosis II nondisjunction… so advanced maternal age).

Mosaicism is 5-10%

Question 9

Three types of birth defects?

Answer 9

1. Deformation - forms normally initially but somewhere in development there is a physical influence that changes the structure. Component parts are there.
2. Disruption - Underlying genetic programming is normal but an event (like a blood clot) damages the structure so that the end result is that all or part of the structure is missing
3. Malformation - underlying genetic programming is faulty

Question 10

What mechanisms lead to malformation?

Answer 10

Syndromes, sequences, and associations

Question 11

Syndrome

Answer 11

Distinct, recognizable collection of anomalies; single underlying etiology for that individual

Question 12

Sequence

Answer 12

Grouping of linked anomalies, cascade effect

Initial, primary problem/defect leads to additional, secondary problems

Question 13

Association

Answer 13

Non-random, co-occurrence of anomalies; they occur together in the same individual more often than expected by chance

may represent an unidentified syndrome

Question 14

When should you consider a genetics referral?

Answer 14

When there is significant deviation from typical physical and/or intellectual development

(keeping in the person in context of familial and ethnic/racial traits)

Question 15

Risk factors for fetal aneuploidy?

Answer 15

positive family or personal history, increased maternal age, structural fetal malformations

Question 16

characteristics of an effective screening test?

Answer 16

simple to administer, highly sensitive, non-invasive, inexpensive

Question 17

What are principal markers on an ultrasound associated with fetal aneuploidy?

Answer 17

absent nasal bone, thickened nuchal fold, and echogenic bowel

Question 18

Fetal screening tests organized by timing?

Answer 18

NIPS (10 wks)
NT Screen (12-13 wks)
Quadscreen (15-18 wks)
Ultrasound (16-20 wks)

Question 19

Definitive diagnostic tests organized by timing?

Answer 19

CVS (10-12 wks)
Amnio (15-16 wks)
Cordocentesis (after 20 wks)

Question 20

Omphalocele and/or NTD on an ultrasound are associated with what aneuploidy?

Answer 20

Trisomies

Question 21

Duodenal atresia and cardiac malformation on an ultrasound are associated with what aneuploidy?

Answer 21

Trisomy 21

cardiac also Trisomy 18

Question 22

Cystic hygroma on an ultrasound is associated with what aneuploidy?

Answer 22

45X (Turner Syndrome)

or Trisomy 21!

Question 23

Holoprosencephaly on an ultrasound is associated with what aneuploidy?

Answer 23

Trisomy 13

Question 24

When is it okay to have a screening test that has low specificity but high sensitivity?

Answer 24

If it can be followed by a test with high specificty