Antenatal and postnatal screening Flashcards
What is antenatal and postnatal screening?
They are a variety of techniques that are used to monitor the health of the mother, developing foetus and baby.
Why is antenatal screening done?
To identify the risk of a disorder so that further tests and a prenatal diagnosis can e offered.
What are the names of the ultrasound scans that are given to pregnant women?
- Dating scan
- Anomaly scan
When does the dating scan take place?
Between 8-14 weeks
When does the anomaly scan take place?
18-20 weeks
What does the dating scan do?
Determines the stage of pregnancy and due date.
What does the anomaly scan do?
It may detect serious physical abnormalities in the foetus.
What is amniocentesis?
Its a procedure that involves the collection of foetal cells contained within amniotic fluid.
when is amniocentesis carried out?
Between the 15th and 20th week of pregnancy
What is an advantage of amniocentesis?
it is used to detect genetic or chromosomal abnormalities of the foetus.
What is a disadvantage of amniocentesis?
the procedure carries a risk of miscarriage.
What is chorionic villus sampling?
Its a procedure that removes a small sample of cells from the placenta.
When is chorionic villus sampling carried out?
11th to 14th week of pregnancy
Whats an advantage of CVS?
Its used to detect genetic or chromosomal abnormalities of the foetus and can be performed earlier than amniocentesis.
Whats a disadvantage of CVS?
It carries a higher risk of miscarriage than amniocentesis does.
What is a karyotype?
It shows an individuals chromosomes arranged as homologous pairs
describe autosomal recessive disorders:
They are expressed very rarely and often skip generations and it affects both males and females equally
Whats an example of an autosomal recessive disorder?
cystic fibrosis
Describe a autosomal dominant disorder:
Affected individuals will always have an infected parent, it affects both males and females equally, and when the trait does not appear in a branch it won’t appear in future generations
What is an example of an autosomal dominant disorder?
Huntingtons disease
Describe incomplete dominance disorders:
Carriers of the allele show a mild form or intermediate form of the trait, as neither allele is completely dominant over the other.
What is an example of an incomplete dominance disorder?
Tay Sachs disease
Describe sex-linked recessive single gene disorders:
Occurs in x chromosomes only, they always affect more males than females. None of the sons of affected males are affected but grandsons can show the trait.
What is an example of a sex-linked recessive single gene disorder?
colour blindness or haemophilia
What causes phenylketonuria?
Its caused by a substitution mutation meaning that an enzyme converts phenylalanine to tyrosine is non-functional.
How do you treat Phenylketonuria?
By putting the individual on a restrictive diet.
What is the postnatal diagnostic test for PKU called?
Guthrie test or the heel prick test
Describe the heel prick test:
The heels of new born babies are pricked and samples of blood are pressed onto the test card and analysed for levels of phenylalanine.
