Genetics Flashcards
(13 cards)
8 weeks gestation genetics screening, which foetal genetic disorders are routinely screened for?
1st trimester trisomy screen:
serum markers and nuchal thickness
Trisomy 13 - Patau syndrome
Trisomy 18 - Edwards syndrome
Trisomy 21 - Down syndrome
What is non-invasive prenatal testing (NIPT)?
It is a screening test that has a positive predictive value > 90% (not diagnostic)
checks foetal DNA from the placenta that are present in mother’s blood
Accuracy affected by factors like mom’s BMI
If someone has a positive NIPT, what is the next step?
Offer a diagnostic test, which is chorionic villi sampling (11-14 weeks) or amniocentesis (>15 weeks)
Amniocentesis is the more diagnostic test
CVS is based on the placental DNA, but there might be a genetic variant that is only present in the cell mass of placenta and not in the foetus
A TOP is only offered if we are fully convinced there are NO mosaicism
What is the next screening test after amniocentesis test for trisomy?
Fetal Chromosome microArray (down to a few hundred basepairs)
What is the TORCH screen used for?
Check for congenital infections
What is fetal MRI used for?
a suspected MSK issue like with the spine
When would you check maternal Ro and La antibodies?
If there is foetal heart block
When you send for a genetic test, you are expected to know what you are looking for
What is the biggest problem for doing a whole exome sequencing for a foetus?
You would identify lots of unknown variants
If at trimester screen the baby is small for dates, what is the primary concern?
Assess maternal wellbeing and screen for pre-eclampsia
A rhesus -ve pregnant women has anti-D antibodies identified at booking. Her partner is heterozygous D +ve. What is the most appropriate next test?
To look for foetal anaemia, we can perform a middle cerebral artery Doppler (there would be increased blood flow in this artery in an attempt to compensate for the low/abnormal RBC
What is NIPD?
