Genetics and Foetal Medicine

Question 1

How is trisomy 21 screened for in the first trimester?

Answer 1

By serum markers and nuchal thickness

Question 2

What are some features of NIPT screening testing?

Answer 2

Positive predictive value >90%
Looks for free foetal DNA in maternal circulation
Affected by maternal BMI

Question 3

When can diagnostic testing be done for trisomy 21?

Answer 3

Chorionic villus sampling = from 11-14 weeks

Amniocentesis = after 15 weeks

Question 4

What is confined placental mosaicism?

Answer 4

Foetal DNA in maternal circulation comes from the placenta (not the foetus)

Question 5

What is the first line investigation for chromosomal abnormalities?

Answer 5

Chromosome micro-array = higher resolution but only detects imbalance

Question 6

What must you know before doing amniocentesis?

Answer 6

What you are testing for

Question 7

What is the biggest problem with whole exome sequencing?

Answer 7

It identifies lots of unknown variants

Question 8

How much of the genome is exons?

Answer 8

Only 2-3%

Question 9

What is the first line treatment for a foetal anencephaly diagnosed at 26 weeks?

Answer 9

Syntocinon