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POM GENETICS > Genetic Testing > Flashcards

Genetic Testing Flashcards

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1
Q

When is a nuchal scan done?

A

10-14 weeks gestation

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2
Q

What 5 things can a Nuchal Scan do?

A
  1. date the pregnancy
  2. diagnose multiple pregnancies
  3. disgnose major fetal abnormalities
  4. diagnose early miscarriage
  5. assess the risk of down syndrome
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3
Q

What technique is used to assess the risk of down syndrome?

A

Nuchal translucency scan

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4
Q

At how many weeks is a mid trimester scan done?

A

20-22 weeks

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5
Q

What is the purpose of the mid trimester anomaly scan?

A

To take a more detailed look at specific organs like heart, brain, spinal cord and to check for 11 rare conditions

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6
Q

What are the two conditions under which prenatal testing is arranged?

A

If the nuchal scan or mid trimester scan brings up an increased risk of down syndrome, or parents are carriers for a specific condition

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7
Q

What is measured during a Nuchal Translucency test?

A

The thickness of fluid at the back of the foetal neck

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8
Q

A nuchal translucency if more than how many mm indicates a problem?

A

anything more than 3mm

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9
Q

If the nuchal thickness is >3mm, what 3 things can this indicate?

A
  1. Increased risk of down syndrome
  2. Birth defects
  3. Chromosomal abnormalities
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10
Q

What birth defects can arise from an increase nuchal translucency?

A
  1. Cardiac abnormalities
  2. Pulmonary abnormalities
  3. Renal defects
  4. Abdominal wall defects
  5. Skeletal dysplasias
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11
Q

What is linked to nuchal translucency which increases the risk of the baby having down synrdome?

A

Maternal age

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12
Q

What type of test is a nuchal translucency scan?

A

A screening test

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13
Q

What are the 4 main aims of prenatal testing?

A
  1. Inform / prepare parents
  2. Allow for the termination of pregnancy if necessary
  3. Help manage the remainder of the pregnancy
  4. Allow possible in utero treatment
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14
Q

What type of scan is used to look at the fetal organs in more detail?

A

A fetal MRI

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15
Q

What serum markers are tested in maternal serum screening?

A

Serum markers for trisomy 18, 21 and neural tube defects

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16
Q

How do serum markers in the mothers blood for conditions like neural tube defects get there?

A

Leak from placenta into mothers blood

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17
Q

When is the 1st trimester maternal serum screening and NT measurement done at?

A

11-14 weeks

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18
Q

What is PAPP A?

A

Hormone made by placenta during pregnancy

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19
Q

What might a low PAPP A suggest?

A

Defective / smaller placenta

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20
Q

When are PAPP A levels measured?

A

11-14 weeks

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21
Q

What is measured during the 2nd trimester maternal serum screen?

A

AFP, UE3 and hCG

22
Q

What does cell free foetal DNA screening do?

A

Analyses the placental DNA in maternal plasma

23
Q

When is cffDNA first ever detectable?

A

4-5 weeks gestation

24
Q

When is the Cell-Free Foetal DNA reading most accurate?

A

9 weeks

25
Q

What three conditions can you be pre-natally tested for for free on the NHS?

A
  1. Apert Syndrome
  2. Achondroplasia
  3. Thanatophoric dysplasia
26
Q

What gene is detected on the Y chromosome in sexting tests?

A

The SRY gene = males

27
Q

In what instance is sexing offered?

A

when there is an X-linked condition in the family - males more at risk so if the baby is male, then go on to pre natal tests to double check

28
Q

What are the two types of invasive tests required?

A

Amniocentesis and Chorionic Villus Sampling

29
Q

Where are the chorionic villi found?

A

As part of the developing placenta

30
Q

Why is a sample of the chorionic villi taken?

A

It has the same DNA as foetus

31
Q

Why is CVS chosen over amniocentesis?

A

It allows the parents to have their results earlier than amnio

32
Q

When is CVS done?

A

11-14 weeks, usually at 12

33
Q

How are CVS samples taken?

A

Transvaginally or transabdominally

34
Q

At what stage is amniocentesis done at?

A

from 16 weeks

35
Q

What does amniocentesis involve?

A

Sample of amniotic fluid is taken as it contains foetal cells

36
Q

What are the 3 risks associated with Amniocentesis?

A
  1. Rh sensitisation
  2. Miscarriage
  3. Infection
37
Q

What happens to cffDNA in women with a higher BMI?

A

Lower cffDNA count as they have more of their own DNA

38
Q

What is the limitation of non-invasive prenatal tests involving twins?

A

not possible to tell which foetus the DNA is from

39
Q

What are the benefits of non-invasive pre-natal testing over invasive techniques

A
  1. No risk of miscarriage
  2. Less impactful on the baby / mother
  3. Less expertise is needed to perform the tests
  4. Can be done earlier than invasive techiques
40
Q

What is the purpose of a CGH array?

A

looks for imbalances in chromosomes that may lead to diseases

41
Q

What may be done after a CGH array if chromosomal imbalances are found?

A

Testing of parents to see if they are carriers

42
Q

What is a trio exome test?

A

A full genetic sequencing

43
Q

When are trio exome tests offered?

A

When previous pregnancies showed serious anomalies eg brain, skeletal and heart

44
Q

What are the four potential options for reproduction?

A

Conceive naturally
Adopt
Use egg / sperm donors
Pre-Implantation Genetic Diagnosis - IVF

45
Q

when is pre-implantation genetic diagnosis used?

A

For conditions caused by single faulty gene to reduce the amount of non-embryo DNA (including sperm DNA) which could make the risk of a wrong diagnosis higher

46
Q

At what stage is the embryo biopsied?

A

8 cell stage

47
Q

What is an intracytoplasmic sperm injection?

A

When a single sperm is injected into the center of each egg

48
Q

What are the downsides of PIGD?

A
  1. Can be emotionally stressful
  2. Lengthy and expensive process
  3. Success rate is low - around 30% per cycle
49
Q

How many round of PIGD are couples usually funded for provided they fit the criteria?

A

3

50
Q

What is the role of a genetic counsellor in prenatal testing?

A
  1. Arrange CVS and amnio
  2. Provide emotional support for parents
  3. Provide information on termination options
  4. Facilitate decision making
  5. give results of tests
  6. Discuss recurrence risks and plans for future pregnancies

POM GENETICS (9 decks)

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