Genetics, Pregnancy and Child Health

Question 1

What can all pregnant women be screened for at 11 weeks gestation?

Answer 1

Down’s syndrome

Question 2

What is needed to do DNA/chromosome testing on a baby in utero?

Answer 2

Tissue with the same genetic make up = placenta (chorionic villus biopsy), skin/urine cells (amniocentesis)

Question 3

When can DNA/chromosome testing be done?

Answer 3

CVS = at 11.5 weeks
Amniocentesis = at 15+ weeks

Question 4

What is sampled in non-invasive prenatal testing?

Answer 4

Free foetal DNA in maternal circulation (only 10% comes from foetus)

Question 5

What can non-invasive prenatal testing be used for?

Answer 5

Trisomy testing and sex determination

Question 6

Does amniocentesis carry any risks?

Answer 6

Yes = 1% chance of causing miscarriage

Question 7

What is confined placental mosaicism?

Answer 7

When the placenta carries a genetic difference that the foetus doesn’t carry (e.g placenta may have chromosome trisomy that is absent in foetus)

Question 8

What kind of result in non-invasive prenatal testing would indicate foetal Down’s syndrome?

Answer 8

Slight excess in chromosome 21 in maternal serum

Question 9

Why is screening during pregnancy deemed acceptable?

Answer 9

Allows early recognition, gives parents time to adjust to diagnosis before birth, patients consider it a part of their healthcare service

Question 10

How is termination of pregnancy carried out?

Answer 10

Surgical termination before 13 weeks

Induction of pregnancy thereafter

Question 11

In what scenarios would their be no time limit on getting a termination of pregnancy?

Answer 11

If there is risk of serious abnormality in the child or to the health of the mother

Question 12

What causes Edward’s syndrome?

Answer 12

Trisomy of chromosome 18 = poor prognosis, often born premature, very small size and cardiac defects

Question 13

What are some influences that may cause parents to decide to get a termination of pregnancy?

Answer 13

Social and religious views, previous experience, perception of disease

Question 14

Are terminations of pregnancy usually seen in wanted or unwanted pregnancy?

Answer 14

Usually for a wanted pregnancy

Question 15

How does known haemophilia in a foetus impact their future management?

Answer 15

More foetal blood tests requested to confirm diagnosis

Vitamin K isn’t given via IM injection

Question 16

What is invasive testing used to identify, and what methods are used?

Answer 16

Single gene changes = PCR, next generation sequencing

Chromosome abnormalities = chromosomal microarray

Question 17

What does aCGH identify?

Answer 17

How much DNA a person has (i.e how much of a certain chromosome is present)

Question 18

What are the benefits and issues with chromosome microarray?

Answer 18

Benefit = high resolution, rapid, technically easier
Issues = also finds polymorphisms, may make incidental findings

Question 19

What are some indications for invasive testing?

Answer 19

High risk of chromosomal trisomy on screening
Positive non-invasive test results
Foetal abnormality on scanning
If parent has balanced chromosome rearrangement

Question 20

What are some foetal abnormalities seen on scanning that may need further invasive testing?

Answer 20

Small size, increased nuchal thickness, malformations

Question 21

What are some features of a floppy baby?

Answer 21

Like a rag doll, lack of head control, increased ROM, frog legged, possible breathing difficulties

Question 22

What are some locations that may be affected to cause floppiness in a baby?

Answer 22

Cortex, spinal cord, anterior rami/motor neurons, neuromuscular junction, muscle

Question 23

What site is most commonly implicated in causing floppiness

Answer 23

Central causes (i.e brain)

Question 24

How many polymorphisms do most people have?

Answer 24

3 million

Question 25

What kind of mutation is implicated in a significant proportion of severe presentations in neonates?

Answer 25

De novo mutations