Genetics/PGT

Question 1

When might a clinical geneticist be required in pregnancy?

Answer 1

Family history that can affect the pregnancy
Unexpected finding in pregnancy
Previous pregnancy/child has genetic issues

Question 2

Genetic testing available in pregnancy?

Answer 2

Chorionic villous biopsy
Amniocentesis
Non-invasive pre-natal testing

Question 3

What gestation can chorionic villous biopsy be done in pregnancy?

Answer 3

11.5 weeks

Question 4

Possible problem with chorionic villous biopsy for picking up genetic problems?

Answer 4

Risk of confined placental mosaicism - this is when the placenta has different cells than the baby does

Question 5

What is confined placental mosaicism?

Answer 5

The placenta has different cells than the baby does

Question 6

What week gestation can you do amniocentesis?

Answer 6

15+ weeks

Question 7

What week gestation can you do non-invasive pre-natal testing?

Answer 7

8+ weeks

Question 8

What can non-invasive pre-natal testing be used for?

Answer 8

trisomy testing
sex determination for x-linked disorders

Question 9

What does non-invasive pre-natal testing test?

Answer 9

Free foetal DNA in the maternal circulation

Question 10

What is usually the first line genetic analysis test used if there is a problem found in pregnancy?

Answer 10

Chromosome microarray (i.e. arrayCGH)

Question 11

What does arrayCGH do?

Answer 11

Looks at chromosomes and spots imbalances (i.e. extra or missing things)

Question 12

What is a potential problem when using a whole genome test?

Answer 12

It will also pick up polymorphisms instead of just mutations

Question 13

When would chromosomal analysis be required?

Answer 13

High risk of chromosomal trisomy
Foetal abnormality on scanning
Parent has a balanced chromosomal rearrangement

Question 14

What prenatal screening is there in Scotland?

Answer 14

12 weeks - dating US scan and serum biochemistry

16 weeks - serum screening

20 weeks - detailed scan to look for other foetal abnormalities

Question 15

What is pre-implantation genetic testing?

Answer 15

A test performed to analyse the DNA from oocytes or embryos for HLA typing or for determining genetic abnormalities

Question 16

What is the most common thing that is tested in PGT?

Answer 16

Blastocyst

Question 17

Why is the embryo frozen after it undergoes PGT?

Answer 17

To allow time for the test to be carried out

Question 18

What are the 3 categories of PGT?

Answer 18

PGT-A (aneuploidy)
PGT-SR (structural rearrangements)
PGT-M (monogenic)

Question 19

PGT-A is a diagnostic/screening test?

Answer 19

Screening

Question 20

PGT-SR is a diagnostic/screening test?

Answer 20

Diagnostic

Question 21

PGT-M is a diagnostic/screening test?

Answer 21

Diagnostic

Question 22

What does PGT-A do?

Answer 22

Screens for presence of all 23 pairs of chromosomes

Question 23

What does PGT-SR do?

Answer 23

Detects translocations, inversions and deletions

Question 24

What does PGT-M do?

Answer 24

Detects known inherited disorders

Question 25

Examples of conditions that may be picked up on PGT-M?

Answer 25

Thalassaemia
Sickle cell anaemia
Haemophilia
CF
Huntington’s disease
Fragile X syndrome
BRCA mutations

Question 26

Indications for PGT-A use?

Answer 26

Advanced maternal age
Recurrent implantation failure
Recurrent miscarriages
Severe male factor infertility

Question 27

What is the primary purpose of a screening test?

Answer 27

detect early disease or risk factors for disease in large numbers of apparently healthy individuals

Question 28

What is the purpose of a diagnostic test?

Answer 28

to establish the presence of disease as a basis for treatment decisions in symptomatic or screen positive individuals