Antenatal and postnatal screening

Question 1

What is antenatal and postnatal screening?

Answer 1

They are a variety of techniques that are used to monitor the health of the mother, developing foetus and baby.

Question 2

Why is antenatal screening done?

Answer 2

To identify the risk of a disorder so that further tests and a prenatal diagnosis can e offered.

Question 3

What are the names of the ultrasound scans that are given to pregnant women?

Answer 3

• Dating scan
• Anomaly scan

Question 4

When does the dating scan take place?

Answer 4

Between 8-14 weeks

Question 5

When does the anomaly scan take place?

Answer 5

18-20 weeks

Question 6

What does the dating scan do?

Answer 6

Determines the stage of pregnancy and due date.

Question 7

What does the anomaly scan do?

Answer 7

It may detect serious physical abnormalities in the foetus.

Question 8

What is amniocentesis?

Answer 8

Its a procedure that involves the collection of foetal cells contained within amniotic fluid.

Question 9

when is amniocentesis carried out?

Answer 9

Between the 15th and 20th week of pregnancy

Question 10

What is an advantage of amniocentesis?

Answer 10

it is used to detect genetic or chromosomal abnormalities of the foetus.

Question 11

What is a disadvantage of amniocentesis?

Answer 11

the procedure carries a risk of miscarriage.

Question 12

What is chorionic villus sampling?

Answer 12

Its a procedure that removes a small sample of cells from the placenta.

Question 13

When is chorionic villus sampling carried out?

Answer 13

11th to 14th week of pregnancy

Question 14

Whats an advantage of CVS?

Answer 14

Its used to detect genetic or chromosomal abnormalities of the foetus and can be performed earlier than amniocentesis.

Question 15

Whats a disadvantage of CVS?

Answer 15

It carries a higher risk of miscarriage than amniocentesis does.

Question 16

What is a karyotype?

Answer 16

It shows an individuals chromosomes arranged as homologous pairs

Question 17

describe autosomal recessive disorders:

Answer 17

They are expressed very rarely and often skip generations and it affects both males and females equally

Question 18

Whats an example of an autosomal recessive disorder?

Answer 18

cystic fibrosis

Question 19

Describe a autosomal dominant disorder:

Answer 19

Affected individuals will always have an infected parent, it affects both males and females equally, and when the trait does not appear in a branch it won’t appear in future generations

Question 20

What is an example of an autosomal dominant disorder?

Answer 20

Huntingtons disease

Question 21

Describe incomplete dominance disorders:

Answer 21

Carriers of the allele show a mild form or intermediate form of the trait, as neither allele is completely dominant over the other.

Question 22

What is an example of an incomplete dominance disorder?

Answer 22

Tay Sachs disease

Question 23

Describe sex-linked recessive single gene disorders:

Answer 23

Occurs in x chromosomes only, they always affect more males than females. None of the sons of affected males are affected but grandsons can show the trait.

Question 24

What is an example of a sex-linked recessive single gene disorder?

Answer 24

colour blindness or haemophilia

Question 25

What causes phenylketonuria?

Answer 25

Its caused by a substitution mutation meaning that an enzyme converts phenylalanine to tyrosine is non-functional.

Question 26

How do you treat Phenylketonuria?

Answer 26

By putting the individual on a restrictive diet.

Question 27

What is the postnatal diagnostic test for PKU called?

Answer 27

Guthrie test or the heel prick test

Question 28

Describe the heel prick test:

Answer 28

The heels of new born babies are pricked and samples of blood are pressed onto the test card and analysed for levels of phenylalanine.