T2 L13 Prenatal screening

Question 1

What is screening?

Answer 1

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

Question 2

What is the 10-14 week scan for?

Answer 2

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

Question 3

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

Answer 3

Chorionicity

Question 4

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

Answer 4

Identical twins

Babies share a placenta

Question 5

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

Answer 5

Dichorionic

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

Question 6

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

Answer 6

Spina bifida
Anencephaly
Exomphalos & gastroschisis
Bladder outflow obstruction

Question 7

What does a diagnostic test do?

Answer 7

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

Question 8

What are the types of diagnostic tests?

Answer 8

Chorionic villus sampling

Amniocentesis

Question 9

What is CVS carried out from?

Answer 9

11 weeks

Question 10

When is amniocentesis carried out from?

Answer 10

15 weeks

Question 11

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

Answer 11

Maternal age + nuchal translucency + PAPPA BhCG

Question 12

What are some influencing factors for combined screening?

Answer 12

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

Question 13

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

Answer 13

Phoned within 3 working days

Question 14

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

Answer 14

Letter within 2 weeks

Question 15

What is the detection rate for combined screening?

Answer 15

82%

Question 16

What is the screen positive rate for combined screening?

Answer 16

2.7%

Question 17

What does an increased nuchal translucency increase the chance of?

Answer 17

Chromosomal anomaly
Cardiac anomaly
Syndromes

Question 18

What should be offered if there is increased nuchal translucency?

Answer 18

Karyotyping - array CGH
Foetal cardiac scan
Anomaly scan

Question 19

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

Answer 19

Maternal age
Gestational age
Smoking
Weight
Ethnicity
Maternal serum markers

Question 20

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

Answer 20

Decreased UE3
Decreased AFP
Increased inhibin A
Increased BHCG

Question 21

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

Answer 21

75%

Question 22

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

Answer 22

5.5%

Question 23

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

Answer 23

Monochorionic = 80%
Dichorionic = 40-50%

Question 24

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

Answer 24

3% in monochorionic and dichorionic twins

Question 25

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

Answer 25

Do nothing
Diagnostic invasive testing
Non-invasive prenatal testing

Question 26

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

Answer 26

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?

Question 27

Describe NIPT

Answer 27

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%

Question 28

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

Answer 28

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

Question 29

What considerations are there for NIPT on the NHS?

Answer 29

Stem cell therapy
Egg donation
IVF

Question 30

What are the advantages of NIPT?

Answer 30

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

Question 31

What information should be given if trisomy 21 is diagnosed?

Answer 31

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

Question 32

What are the options if the condition is diagnosed?

Answer 32

Continue
Continue and adoption
Terminal - medical or surgical

Question 33

What are some support options if the condition is diagnosed?

Answer 33

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

Question 34

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

Answer 34

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