T2 L13 Prenatal screening Flashcards

1
Q

What is screening?

A

Identifies apparently healthy people who may be at increased risk of a disease or condition, enabling earlier treatment or informed decisions

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2
Q

What is the 10-14 week scan for?

A
Viability
Accurate dating
Detect multiple pregnancies
Diagnose structural abnormality
Screen for chromosomal conditions
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3
Q

What is the main determinant of foetal outcome in a multiple pregnancy?

A

Chorionicity

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4
Q

What does it mean for the babies if there is a T-sign on the U/S?

A

Identical twins

Babies share a placenta

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5
Q

What does it mean for the babies if there is a lambda sign on the U/S?

A

Dichorionic

There is an extension of placental tissue into base of intertwin membrane

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6
Q

Give examples of structural abnormalities diagnosed on the 10-14 week scan

A

Spina bifida
Anencephaly
Exomphalos & gastroschisis
Bladder outflow obstruction

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7
Q

What does a diagnostic test do?

A

Gives definitive information on the foetal chromosomes by confirming the presence of an extra chromosome or the absence of a chromosome

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8
Q

What are the types of diagnostic tests?

A

Chorionic villus sampling

Amniocentesis

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9
Q

What is CVS carried out from?

A

11 weeks

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10
Q

When is amniocentesis carried out from?

A

15 weeks

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11
Q

How is the chance of a baby having trisomy 21 and/or trisomy 13/18 calculated from the combined screening test?

A

Maternal age + nuchal translucency + PAPPA BhCG

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12
Q

What are some influencing factors for combined screening?

A
Maternal age
Gestational age
Ethnicity
Smoking
IVF
Multiple pregnancy
Weight
Diabetes
Past history of chromosome abnormality
Foetal sex
Analytical imprecision.
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13
Q

How are results of the combined screening delivered if there is a high risk?

A

Phoned within 3 working days

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14
Q

How are the results of the combined screening delivered if there is low risk?

A

Letter within 2 weeks

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15
Q

What is the detection rate for combined screening?

A

82%

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16
Q

What is the screen positive rate for combined screening?

A

2.7%

17
Q

What does an increased nuchal translucency increase the chance of?

A

Chromosomal anomaly
Cardiac anomaly
Syndromes

18
Q

What should be offered if there is increased nuchal translucency?

A

Karyotyping - array CGH
Foetal cardiac scan
Anomaly scan

19
Q

What considerations are taken into account for the second trimester quadruple test?

A
Maternal age
Gestational age
Smoking
Weight
Ethnicity
Maternal serum markers
20
Q

Describe the results of maternal serum markers in down’s syndrome

A

Decreased UE3
Decreased AFP
Increased inhibin A
Increased BHCG

21
Q

What are the detection rates for the quadruple test in singletons?

A

75%

22
Q

What are the screen positive rates for the quadruple test in singletons?

A

5.5%

23
Q

What are the detection rates for twins in the quadruple test?

A
Monochorionic = 80%
Dichorionic = 40-50%
24
Q

What are the screen positive results for the quadruple test in twins?

A

3% in monochorionic and dichorionic twins

25
Q

What are the main options if the results show a high chance?

A

Do nothing
Diagnostic invasive testing
Non-invasive prenatal testing

26
Q

What questions could be asked to help parents’ decisions if they receive a high chance from the screening test?

A

Could you cope throughout pregnancy not knowing?
How would it be to find out your baby has Downs at birth?
What would be worse: miscarrying a normal baby or finding out at birth that your baby had Downs?
What would you do if you knew for sure your baby had Downs right now? Would you consider termination?

27
Q

Describe NIPT

A

Cell free foetal DNA in maternal blood from 5 weeks
Specific to pregnancy
Test maternal blood from 10 weeks
Aneuploidy: screening for T21 sensitivity & specificity over 99%

28
Q

When should NIPT not be used due to the risk of false positive results?

A
Maternal malignancy
Multiple pregnancy
Blood transfusion within 4 months
Organ transplant
Vanished twin / demised twin
Known chromosome or genetic anomaly in mother
29
Q

What considerations are there for NIPT on the NHS?

A

Stem cell therapy
Egg donation
IVF

30
Q

What are the advantages of NIPT?

A

High detection rates
Low screen positive rates
Reduction in invasive diagnostic testing
Further option for women

31
Q

What information should be given if trisomy 21 is diagnosed?

A

Associated with some level of learning disability. Can’t predict severity pre-birth
Some health conditions are more common
Typical life expectancy is 60+

32
Q

What are the options if the condition is diagnosed?

A

Continue
Continue and adoption
Terminal - medical or surgical

33
Q

What are some support options if the condition is diagnosed?

A
Antenatal screening co-ordinator
National support groups - ARC, DSA, Soft UK, unique
Meet other parents
Obstetric / neonatal / paediatric teams
Genetic counselling
34
Q

What is some pre-screening test information that should be given?

A
Tests are optional
What are we screening for?
What the tests won't tell you
Timing of tests
Communicating results
Invasive tests
Options if abnormality is diagnosed