Prenatal Genetic Testing and Amniocentesis/CVS GT8

Question 1

How long does full karyotyping with G-banding take to get a result?

Answer 1

10-21 days

Question 2

How long does it take to get a result with QF-PCR (for whole chromosome anomalies e.g. trisomy)

Answer 2

48-76 hours

Question 3

Which method of genetic testing can be used to detect submicroscopic deletions or duplications?

Answer 3

Chromosomal microarray analysis (CMA)

Question 4

What are the limitations of chromosomal microarray analysis?

Answer 4

• Can only detect unbalanced chromosomal changes
• May not detect trisomies unless SNP based array performed
• Low level mosaicism may not be detected
• Identifies variants of unknown significance (VOUS)

Question 5

How many women are offered invasive prenatal diagnostic tests?

Answer 5

5%

30,000/yr in the UK

Question 6

At what gestations can CVS and amnio be performed?

Answer 6

CVS: 11+0-13+6

Amnio from 15+0

Question 7

What is the maximum outer gauge of the needle for amniocentesis?

Answer 7

0.9mm

20 gauge

Question 8

What is the rate of miscarriage with invasive testing?

Answer 8

Approx 1%

1.8% in T2 twin pregnancy

Question 9

What is the risk of severe sepsis following invasive testing?

Answer 9

1/1000