Antenatal and Postnatal testing Flashcards
What’s is antenatal screening
Antenatal screening assesses the health of the mother and tests for diseases/. conditions in an embryo/foetus before birth.
what disorders can be identified by antenatal screening?
- Down Syndrome
- Spina Bífida
- Cystic Fibrosis
- Muscular dystrophy
when is the dating scan given and what does it do?
It’s given at 8-14 weeks and is used to determine the stage of pregnancy and the due date of the baby
when is the anomaly scan given and what does it do?
It’s given at 18-20 and is used to detect any physical abnormalities in the developing foetus.
why is the dating scan so important for biochemical tests?
If the stage of pregnancy was wrongly calculated the results would appear skewed and could indicate a problem with the foetus.
what condition could be suggested if the blood concentrations during pregnancy are too high?
a neural tube defect (Spina Bifida)
what condition could be suggested if the blood concentrations during pregnancy are too low?
chromosomal abnormality (Down syndrome)
what would be offered if a positive result came up in biochemical testing?
a diagnostic test
what are the two diagnostic tests?
- Amniocentesis
- Chronic Villus Sampling (CVS)
What are the advantages of of Amniocentesis?
- lower risk of miscarriage
- detects chromosomal abnormalities and neutral tube defects
What are the disadvantages of Amniocentesis?
- carried out later
- cells collected and cultivates takes long (several weeks for karyotype)
What are the advantages of Chronic Villus Sampling?
- carried out earlier (placental tissue collected and cultured into an instant karyotyoe)
What’s are the disadvantages of Chronic Villus Sampling?
- Higher risk of miscarriage
- Detect only chromosomal abnormalities
what Chromosome is affected by Tuner Syndrome and what is the impact
- only one x chromosome
impact: lower fertility rate
what chromosome is affected by klinefelter syndrome and what is the impact?
- 2 x chromosomes and a y chromosome
impact: - lower fertility - slightly feminised physique
What chromosome is affected by Edward’s syndrome and what is it’s impact?
- The 10th chromosome is affected
impact: - organ systems affected - babies tend not to live for longer than a few months
What chromosome is affected by Down Syndrome and what is the impact?
- the 21st set of chromosomes are effected
impact: - lower lifespan - holes in the heart are more common
- learning difficulties
What are the 4 types of single gene disorder? and examples of each one
- Autosomal recessive ( Cystic Fibrosis and Albinism)
- Autosomal dominant (Huntington’s and Chorea)
- Autosomal incomplete dominance ( Sickle Cell Anemia)
- Sex-linked recessive ( Haemophilia)
What are the patterns of inheritance for Autosomal Recessive traits?
- the trait is expressed rarely
- tends to skip generations
- all sufferers have a double recessive genotype
- non-suffers are homozygous dominant or heterozygous
What are the patterns of inheritance for Autosomal dominant?
- appears in every generation
- each sufferer has an effected parent
- when a branch of the family doesn’t express the trait it wont appear in that future line
- affects males and females equally
- all non-sufferers are homozygous recessive
- all sufferers are homozygous are homozygous dominant or heterozygous
What are the patterns of inheritance for Autosomal Incomplete Dominance?
- Fully expressed form occurs rarely
- partially expressed form occurs more frequently
- each sufferer of the fully expressed form has two parents who suffer the partly expressed
- males and females are effected equally
- all non-sufferers are homozygous dominant for the incomplete allele
- there are no recessive alleles
What are the the patterns of inheritance for sex-linked recessive?
- more males effected than females
- none of the sons of an effected male have the trait unless the mum is effected
- some grandsons will show the trait
- all non sufferers are homozygous recessive
- non-suffers are homozygous dominant or heterozygous carriers in females.
why are more males affected by sex-linked recessive mutations?
because the trait will always be expressed on the x chromosome
what is postnatal screening?
Diagnostic tests that occur after the birth to detect the presence of conditions such as phenylketonuria using a blood test.
