Antenatal & postnatal screening

Question 1

Define screening.

Answer 1

The process of identifying apparently healthy individuals for a condition they may be at risk of, so that further investigation and treatment can take place

Question 2

What is the criteria for a disease to be considered for a screening programme?

Answer 2

Wilson and Junger

Is it an important condition (serious, not too rare)

Is there a reliable test?

Is there a good treatment?

Would early intervention improve outcomes?

Is it cost-effective?

Question 3

What are the limitations of a screening programme?

Answer 3

There will always be false negatives and positives

It is not a guarantee that the person will not develop the condition

Question 4

What is a false positive and a false negative?

Answer 4

False positive: they test positive for a disease but they don’t have it

False negative: they test negative but they do have the disease

Question 5

What information should be provided to a patient or parents when consenting for screening?

Answer 5

What condition is being screened for

When and how it’s done

How reliable it is

What options are available to them if the test is positive

Question 6

List the antenatal screening programmes in the UK.

Answer 6

Fetal anomaly screening

Infectious diseases screening of mother

Haemoglobinopathies

Question 7

What are the stages of the fetal anomaly screening programme and when are they done?

Answer 7

1. Combined test (1st trimester) looks at nuchal translucency and maternal serum markers
2. Quadruple test (2nd trimester) only if they haven’t had the combined test,
   looks at serum markers
3. Early USS (10-14 weeks)
4. Later USS (18-21 weeks)

Question 8

Which conditions are screened for in the combined test and how?

When is this test done?

Answer 8

In the 1st trimester: 10-14 weeks

Screening for Down, Patau and Edward’s syndrome

Looks at nuchal translucency (thickness of fluid build up at back of neck)

And some serum markers in maternal blood

• beta HCG
• pregnancy associated plasma protein A

Question 9

What is nuchal translucency and why is it relevant?

Answer 9

Measuring the thickness of fluid build up at the back of the baby’s neck

It’s often thicker in Down, Patau and Edwards syndrome

Question 10

Genetic name for Down, Patau and Edward’s syndrome?

Answer 10

Down: trisomy 21
Patau: trisomy 13
Edward’s: trisomy 18

Question 11

The quadruple test is always done on a pregnant woman. True or false?

Answer 11

False

It’s only done in a late booker, or when the combined test has failed to provide a risk score

Question 12

What does the quadruple test screen for and how?
When is it done?
What is checked?

Answer 12

Down, Patau, Edward’s syndromes

Using maternal blood sample

• alpha fetoprotein
• unconjugated oestriol
• inhibin A
• BHCG

15-20 weeks

Question 13

If the combined or quadruple screen comes back as high risk for one of the trisomy syndromes. What is the next step?

Answer 13

Offer diagnostic tests
Amniocentesis
Chorionic villous sampling

Question 14

Briefly what is amniocentesis?

Answer 14

Taking a sample of amniotic fluid for analysis

Question 15

Briefly what is chorionic villous sampling?

Answer 15

Analysis of cells from chorionic villi on the placenta

Question 16

When is the first USS done in pregnancy? What does it look for?

Answer 16

Between 10-14 weeks

Dates pregnancy
Confirms viability
Multiple pregnancies
Obvious anomales (anencephaly)

Question 17

When is the second USS done in pregnancy? What does it look for?

Answer 17

Between 18-21 weeks

Looks for structural abnormalities
Helps plan for birth (if NICU or special care is needed)

Option of abortion

Question 18

Which diseases are screened for as part of the infectious disease screening?

Answer 18

HIV

Hep B

Syphilis

Question 19

What can be done to help the baby if a mother has Hep B?

Answer 19

Vaccinate the baby soon after birth

Question 20

What can be done to help the baby if a mother has HIV?

Answer 20

Treat mother, improves her prognosis and reduces risk of transmission to baby

Question 21

Which haemoglobinopathies are screened for antenatally?

How is this done?

Answer 21

Autosomal recessive ones

• Thalassaemia
• Sickle cell

A blood test is done of parents to see whether they’re carriers.

Question 22

How will alpha and beta thalassaemia affect the babies?

Answer 22

Alpha thalassaemia is incompatible with life, hydrops fetalis

Beta is life threatening and requires transfusuions regularly

Question 23

List the postnatal screening programmes in the UK?

Answer 23

Newborn blood spot

Hearing

Physical examination

Question 24

When is the newborn blood spot test done? How is it done?

Answer 24

On day 5 of life

Heel prick

Question 25

What diseases are screened for on blood spot?

Answer 25

1. Sickle cell
2. CF
3. Congenital hypothyroidism
4. Phenylketonuria
5. Maple syrup urine disease

6-9. Some very rare metabolic conditions

Question 26

When is the hearing screening done?

Answer 26

Prior to discharge home or within 4 weeks

Question 27

What problems are screened for in the newborn physical examination?

Answer 27

Eye problems
Congenital heart defects
Developmental dysplasia of hips
Undescended testes

Question 28

What are the risks of amniocentesis?

Answer 28

Infection
Miscarriage
Rhesus disease due to mixing of blood
Club foot

Question 29

What drug(s) do you sometimes need to give before, during and after amniocentesis?

Answer 29

Anti-D if differing rhesus status, because amnio causes mixing of maternal and fetal blood

Antibiotics

Question 30

When is chorionic villous sampling and amniocentesis done?

Answer 30

CVS: 11 weeks

Amnio 15 weeks