Unit 6 (K4) - Antenatal and Postnatal screening

Question 1

What is a dating scan used for?

Answer 1

To determine pregnancy stage and due date.

Question 2

When does a dating scan take place?

Answer 2

Between 8 and 14 weeks of pregnancy.

Question 3

What is an anomaly scan used for?

Answer 3

To detect any serious physical abnormalities.

Question 4

When does an anomaly scan take place?

Answer 4

Between 18 to 20 weeks of pregnancy.

Question 5

What is a biochemical test?

Answer 5

This is a routine test on the blood and urine throughout pregnancy to monitor the concentration of marker chemicals.

Question 6

What happens if there is an a-typical concentration during a biochemical test?

Answer 6

This leads to diagnostic testing to determine if the foetus has a medical condition.

Question 7

What is a diagnostic test used for?

Answer 7

To establish whether a person is suffering a specific condition or disorder.

Question 8

Offer 3 reasons why a diagnostic test may be offered?

Answer 8

1. If any problems emerge from routine screening tests.
2. There is history of genetic disorder(s) in the family.
3. The women is already in a “high risk” category, over 35 years of age.

Question 9

When is an amniocentesis carried out?

Answer 9

Between 14 to 16 weeks of pregnancy.

Question 10

What happens during an amniocentesis?

Answer 10

A small volume of amniotic fluid containing foetal cells is withdrawn. These cells are cultured and chromosomes used to produce a karyotype.

Question 11

When does Chorionic Villus Sampling (CVS) take place?

Answer 11

As early as 8 weeks of pregnancy.

Question 12

What occurs during Chorionic Villus Sampling (CVS)?

Answer 12

Placental cells are withdrawn and these cells are cultured and chromosomes used to produce a karyotype.

Question 13

What are the disadvantages of Amniocentesis and CVS?

Answer 13

1. Amniocentesis carries a slight risk of miscarriage.
2. CVS carries a much higher risk to miscarriage.

Question 14

What is the advantage of Chorionic Villus Sampling (CVS)?

Answer 14

It can be carried out at an earlier stage in pregnancy.

Question 15

What are the indicators that a trait is autosomal recessive?

Answer 15

1. Males and females are affected equally.
2. Trait is rarely expressed.
3. Trait may skip generations.
4. All sufferers are homozygous recessive (cc)
5. Non-sufferers are homozygous dominant (CC) or heterozygous

Question 16

What are the indicators that a trait is autosomal recessive?

Answer 16

1. Males and females are affected equally.
2. Trait is rarely expressed.
3. Trait may skip generations.
4. All sufferers are homozygous recessive (hh)
5. Non-sufferers are homozygous dominant (HH) or heterozygous (Hh).

Question 17

What are indicators that a trait is Autosomal dominant?

Answer 17

1. Trait appears in every generation.
2. Each sufferer has an affected parent.
3. Males and females are affected equally.
4. Sufferers are homozygous dominant (HH) or heterozygous (Hh).
5. Non-sufferers are homozygous recessive (hh).

Question 18

What are indicators that show autosomal incomplete dominance?

Answer 18

1. Fully expressed form occurs relatively rarely.
2. The partially expressed is much more frequent.
3. Each sufferer of the fully expressed form has two parents that suffer from partly expressed form.
4. Sufferers that are fully expressed are homozygous for the other incompletely dominant allele (SS).
5. Sufferers of the partly expressed are heterozygous (HS).
6. Males and females are affected equally.

Question 19

What are indicators of a sex-linked recessive trait?

Answer 19

1. Many more males affected than females.
2. None of the sons of an affected male show the trait.
3. All sufferers are homozygous recessive (hh).
4. Non sufferers are homozygous dominant (HH) or heterozygous (Hh).