U2: 12- Ante And Postnatal Screening Flashcards
Name the technique by which high frequency sounds are bounced off the fetus and converted to an image on a computer screen.
Ultrasound imaging
Name two scans that are produced through ultrasound imaging.
Dating scan and anomaly scan
When is a dating scan produced?
8-14 weeks
What does a dating scan show?
Stage of pregnancy and due date
When is an anomaly scan carried out?
18-20 weeks
What does an anomaly scan show?
Serious physical abnormalities in the fetus
Name a marker chemical that doctors check for the level of in a mother’s urine/blood.
HCG or AFP
If the levels of these marker chemicals are checked at an inappropriate point in the timeline and found to be high/low, this could lead to what two types of false alarm?
False positives and false negatives
If a fetus is wrongly diagnosed as having a condition when it doesn’t then this is what type of mistake?
False positive
If a fetus is wrongly diagnosed as not having a condition when in actual fact it does, then this is what type of mistake?
False negative
What name is given to the type of tests where they look at marker chemical levels and other indicators that look for signs and symptoms of a disorder but does not tell definitively that the fetus has the disorder?
Screening test
What name is given to a definitive test that establishes without doubt that the fetus has a disorder? It is usually carried out following concerns after a screening test.
Diagnostic test
Name two diagnostic tests.
Amniocentesis and Chorionic Villus Sampling (CVS)
Both diagnostic tests allow the collection of some of the baby’s cells and a photograph of the chromosomes all laid out. What name is given to the visual display of chromosomes?
Karyotype
When is amniocentesis carried out?
14-16 weeks
Where are the cells taken from during amniocentesis?
Amniotic sac
What is the negative aspect of amniocentesis?
Risk of miscarriage
When is CVS carried out?
As early as 8 weeks
Where are the cells for CVS taken from?
The chorionic villus of the placenta
What are the advantages of CVS over amniocentesis?
CVS is carried out earlier in a pregnancy and if there is any problem then a termination can be considered much earlier when it is less traumatic. If parents wait until 14-16 weeks as with amniocentesis then it is much more traumatic.
What name is given to the charts used by genetic counsellors to assess the degree of risk in passing on a genetic disorder to children?
Pedigree chart/family tree
What does a line through a symbol on a pedigree chart show?
The person has died
Which symbol is used to represent a female?
A circle
Which symbol is used to represent a male?
A square
Autosomal recessive inheritance
A condition carried on the autosomes:
• relatively rarely expressed
• skips generations
• occurs more when there is a consanguineous marriage
Autosomal dominant inheritance
Condition carried on the autosomes:
• appears every generation
• each person affected has a parent who suffered the condition
• once the condition is lost from a branch of the tree it is lost altogether from that branch
Autosomal incomplete dominance
A condition carried on the autosomes:
• both alleles are expressed together
• ⬆️ this is the most common phenotype
• males and females affected in equal numbers
Sex-linked recessive inheritance
Condition carried on sex chromosomes:
• more males than females affected
• none of the affected males have sons with the trait
Name a condition whereby a baby is unable to change the amino acid phenylalanine into tyrosine?
Phenylketonuria (PKU)
When is the test for phenylketonuria carried out in babies?
A few days after birth
What name is given to the type of testing that occurs in babies after they are born?
Postnatal screening
