Downs Syndrome Screening

Question 1

Down’s syndrome

Answer 1

Trisomy 21

Gives dysmorphic features

Question 2

Purpose of Down’s syndrome screening

Answer 2

Decide which women should receive more invasive tests to establish a definitive diagnosis

Question 3

What does a Down’s syndrome screening include

Answer 3

USS measurements from the fetus - nuchal translucency

Mother’s age and blood results:

• beta-HCG– a higher result indicates a greater risk
• Pregnancy‑associated plasma protein‑A (PAPPA) – a lower result indicates a greater risk

Question 4

Combined Test

Answer 4

First line and the most accurate screening test

Performed between 11 and 14 weeks gestation

Ultrasound - nuchal translucency
Maternal blood tests

Question 5

Nuchal translucency

Answer 5

Nuchal thickness > 6mm - higher risk of Down’s syndrome

Question 6

Beta HCG

Answer 6

Higher result indicates a greater risk

Question 7

Pregnancy‑associated plasma protein‑A (PAPPA)

Answer 7

Lower result indicates a greater risk

Question 8

Triple Test

Answer 8

Between 14 and 20 weeks gestation.

Maternal blood tests:

Beta-HCG – a higher result indicates greater risk
Alpha-fetoprotein (AFP) – a lower result indicates a greater risk
Serum oestriol (female sex hormone) – a lower result indicates a greater risk

Question 9

When is a combined test performed

Answer 9

11 - 14 weeks

Question 10

When is a triple test performed

Answer 10

If a combined test has not been performed

14 - 20 weeks

Question 11

When is a Quadruple Test performed

Answer 11

14 - 20 weeks gestation

Question 12

What does a quadruple test involve

Answer 12

Beta-HCG – a higher result indicates greater risk

Alpha-fetoprotein (AFP) – a lower result indicates a greater risk

Serum oestriol (female sex hormone) – a lower result indicates a greater risk

Inhibin - A - a higher inhibin A indicates a greater risk

Question 13

Antenatal Down’s syndrome screening risk implications

Answer 13

When the risk of Down’s is greater than 1 in 150 the woman is offered amniocentesis or chorionic villus sampling

Question 14

Chorionic villus sampling (CVS)

Answer 14

USS - guided biopsy of the placental tissue.

Question 15

When is chorionic villus sampling used?

Answer 15

When testing is done earlier in pregnancy (before 15 weeks)

Question 16

Amniocentesis

Answer 16

USS - guided aspiration of amniotic fluid using a needle and syringe

Question 17

When is amniocentesis used

Answer 17

Used later in pregnancy once there is enough amniotic fluid to make it safer to take a sample

Question 18

Non-Invasive Prenatal Testing

Answer 18

Blood test from the mother.

Blood contains some fragments of placental tissue and represent the fetal DNA.

These fragments can be analysed to detect conditions such as Down’s but not definitive