Flashcards in Key Area 2.4 - Ante and Postnatal Screening Deck (17):
What does antenatal screening do?
Identifies the risk of a disorder so that further tests and a prenatal diagnosis can be offered.
What are some common antenatal testing procedures?
Chronic villus sampling
Rhesus antibody testing
What can ultrasound scanners be used to produce?
A pregnancy or gestational dating scan, which is used to determine the stage of pregnancy and the date the baby is due.
Anomaly scan - which is used to detect the presence of serious physical problems in the fetus.
What are biochemical tests used for?
To decent the normal physiological changes of pregnancy. Measuring a substance at the wrong time could lead to a false positive result.
What is diagnostic testing?
Medical conditions can be detected by a range of market chemicals that indicate a condition but need not necessarily be part of the condition
What type of diagnostic testing are there?
What is amniocentesis?
Amniotic fluid drawn from the amniotic sac. Takes several weeks to culture. Results take longer.
What is CVS?
Chronic villus sampling. Gives earlier results. Risk of miscarriage. Sample taken from placenta.
Describe rhesus antibody testing.
- Normally a mothers immune system does not attach the fetus despite its different signature of the mother is Rhesus negative and her baby is Rhesus positive.
- However there is a chance of some blood mixing at birth which causes sensitisation to Rhesus antigens.
- The immune system of the mother then makes the anti-D antibodies and memory cells thag wait for a future invader.
- The fetus can be saved by replacing the Rhesus positive blood with Rhesus negative.
- Alternatively the mother can be injected with anti-D factor, just after birth, to destroy the D antigen.
What is postnatal screening?
Diagnostic testing used to detect metabolic disorders like PKU which is an inborn error of metabolism.
What is PKU?
An inborn error of metabolism. The body can not process excess phenylalanine. If PKU is not detected soon after birth the baby’s mental development is affected. Individuals with high levels of phenylalanine are placed on a restricted diet.
What is genetic screening?
Use of pedigree charts to analyse patterns of inheritance in genetic screening and counselling.
What can genetic screening be used for?
A pattern of inheritance can be revealed by collecting information about a particular characteristic l from family members and the information used to construct a family tree.
Describe autosomal recessive.
Expressed relatively rarely in offspring, affects males and females equally and may skip generations through carriers. E.g. - cystic fibrosis
Describe autosomal dominant.
Can be common in a family. It affects males and females equally and individual cannot carry the condition without being affected. E.g - Huntington’s disease.
Describe autosomal dominance.
The fully expressed form of the condition is rare, the party expressed form is more common and males and females are affected equally. Carriers have a less severe form of the disease, those with two alleles have the more severe form. E.g - sickle cell disease.