U2: 12- Ante And Postnatal Screening

Question 1

Name the technique by which high frequency sounds are bounced off the fetus and converted to an image on a computer screen.

Answer 1

Ultrasound imaging

Question 2

Name two scans that are produced through ultrasound imaging.

Answer 2

Dating scan and anomaly scan

Question 3

When is a dating scan produced?

Answer 3

8-14 weeks

Question 4

What does a dating scan show?

Answer 4

Stage of pregnancy and due date

Question 5

When is an anomaly scan carried out?

Answer 5

18-20 weeks

Question 6

What does an anomaly scan show?

Answer 6

Serious physical abnormalities in the fetus

Question 7

Name a marker chemical that doctors check for the level of in a mother’s urine/blood.

Answer 7

HCG or AFP

Question 8

If the levels of these marker chemicals are checked at an inappropriate point in the timeline and found to be high/low, this could lead to what two types of false alarm?

Answer 8

False positives and false negatives

Question 9

If a fetus is wrongly diagnosed as having a condition when it doesn’t then this is what type of mistake?

Answer 9

False positive

Question 10

If a fetus is wrongly diagnosed as not having a condition when in actual fact it does, then this is what type of mistake?

Answer 10

False negative

Question 11

What name is given to the type of tests where they look at marker chemical levels and other indicators that look for signs and symptoms of a disorder but does not tell definitively that the fetus has the disorder?

Answer 11

Screening test

Question 12

What name is given to a definitive test that establishes without doubt that the fetus has a disorder? It is usually carried out following concerns after a screening test.

Answer 12

Diagnostic test

Question 13

Name two diagnostic tests.

Answer 13

Amniocentesis and Chorionic Villus Sampling (CVS)

Question 14

Both diagnostic tests allow the collection of some of the baby’s cells and a photograph of the chromosomes all laid out. What name is given to the visual display of chromosomes?

Answer 14

Karyotype

Question 15

When is amniocentesis carried out?

Answer 15

14-16 weeks

Question 16

Where are the cells taken from during amniocentesis?

Answer 16

Amniotic sac

Question 17

What is the negative aspect of amniocentesis?

Answer 17

Risk of miscarriage

Question 18

When is CVS carried out?

Answer 18

As early as 8 weeks

Question 19

Where are the cells for CVS taken from?

Answer 19

The chorionic villus of the placenta

Question 20

What are the advantages of CVS over amniocentesis?

Answer 20

CVS is carried out earlier in a pregnancy and if there is any problem then a termination can be considered much earlier when it is less traumatic. If parents wait until 14-16 weeks as with amniocentesis then it is much more traumatic.

Question 21

What name is given to the charts used by genetic counsellors to assess the degree of risk in passing on a genetic disorder to children?

Answer 21

Pedigree chart/family tree

Question 22

What does a line through a symbol on a pedigree chart show?

Answer 22

The person has died

Question 23

Which symbol is used to represent a female?

Answer 23

A circle

Question 24

Which symbol is used to represent a male?

Answer 24

A square

Question 25

Autosomal recessive inheritance

Answer 25

A condition carried on the autosomes:
• relatively rarely expressed
• skips generations
• occurs more when there is a consanguineous marriage

Question 26

Autosomal dominant inheritance

Answer 26

Condition carried on the autosomes:
• appears every generation
• each person affected has a parent who suffered the condition
• once the condition is lost from a branch of the tree it is lost altogether from that branch

Question 27

Autosomal incomplete dominance

Answer 27

A condition carried on the autosomes:
• both alleles are expressed together
• ⬆️ this is the most common phenotype
• males and females affected in equal numbers

Question 28

Sex-linked recessive inheritance

Answer 28

Condition carried on sex chromosomes:
• more males than females affected
• none of the affected males have sons with the trait

Question 29

Name a condition whereby a baby is unable to change the amino acid phenylalanine into tyrosine?

Answer 29

Phenylketonuria (PKU)

Question 30

When is the test for phenylketonuria carried out in babies?

Answer 30

A few days after birth

Question 31

What name is given to the type of testing that occurs in babies after they are born?

Answer 31

Postnatal screening