ANTENATAL SCREENING/DIAGNOSTICS

Question 1

What conditions are tested?

Answer 1

• sickle cell - trisomy 21 (Down’s syndrome)
• beta thalessemia - trisomy 18 (Edwards)
• cystic fibrosis - trisomy 18 (Patau
• cleft palate

Question 2

What is trisomy 21? And when is testing done?

Answer 2

Down’s syndrome - born with extra chromosome
Testing at 10-14 weeks

Question 3

What is trisomy 18? And when is testing done?

Answer 3

Edwards syndrome - born with three copies of chromosome 18 instead of two
10 - 14 weeks

Question 4

What is trisomy 13? And when is testing done?

Answer 4

Patau syndrome - three copies of chromosome 13 instead of two
10-14 weeks

Question 5

What are the three serum bio markers used for T21, 18 and 13?

Answer 5

Hcg (human chorionic gonadotropin)
Pregnancy associated plasma protein
Alpha fetoprotein

Question 6

What is a nuchal translucency ultrasound?

Answer 6

NT thickness is a measure of fluid at the back of the foetal neck (less than 3.5mm is normal)

Question 7

What are the diagnostic tests for antenatal tests?

Answer 7

• chorionic villus sampling
• amniocentesis
• cordocentesis
• preimplantation genetic testing

Question 8

What is chorionic villus sampling?

Answer 8

Removes and tests a small sample of cells from the placenta at 11-14 weeks

Question 9

What is amniocentesis?

Answer 9

removed and tests cells from amniotic fluid (surrounds baby) at 15-20 weeks

Question 10

What is cordocentesis?

Answer 10

collects a sample of blood from foetus umbilical cord to detect blood disorders or genetic mutations at 17+ weeks

Question 11

What is preimplantation genetic testing?

Answer 11

identifies genetic conditions in embryos created by IVF - a few cells removed from pre implantation embryo at blastocyst stage

Question 12

What is PCR after amniocentesis?

Answer 12

DNA from amniocentesis can be detected using PCR to test for conditions such as sickle cell, beta thalessimia

Question 13

What is fluorescent in situ hydbridisation?

Answer 13

Test that identifies chromosomal abnormalities by evaluating presence or absence of flourescent signals in metaphase chromosomes (anueploidy)

Question 14

What is multi - plex FISH?

Answer 14

A test that allows all 24 chromosomes (autosomes and 2 sex) to be highlighted instead of just a few

Question 15

What is G banding karoytping?

Answer 15

Identifies chromosomes abnormalities and creates characteristic banding patterns for large scale abnormalities

Question 16

What is comparative genomic hybridisation?

Answer 16

Detects chromosome abnormalities from small changes and detects variants of unknown significance using microarrays