Antenatal And Postnatal Screening Flashcards
(20 cards)
What can be used to monitor the health of the mother, developing foetus and baby?
A variety of techniques/tests
What does antenatal screening do?
It identifies the risk of a disorder so that further tests and a prenatal diagnosis can be offered
What are the four types of routine initial tests carried out on a pregnant woman?
Height and weight(BMI)
Blood pressure
Blood and urine tests
Medical history
What are the two types of antenatal screening?
Ultrasound imaging
Blood and urine tests
For ultrasound imaging what are the two types of ultrasound scans pregnant woman are given?
Dating scans
Anomaly scans
What are dating scans?
They determine pregnancy stage and due date
They’re also used with tests for marker chemicals which vary normally during preganancy
(Between 8-14 weeks)
What are anomaly scans?
They detect serious physical abnormalities in the foetus
(Between 18-20 weeks)
What are blood and urine tests?
Routine blood and urine tests are carried out throughout pregnancy to monitor the concentrations of marker chemicals
Measuring a chemical at the wrong time could lead to a false positive result
An aytypical chemical concentration can lead to diagnostic testing to determine if the foetus has a medical condition
Example-high levels of HGC normal at start of pregnancy but if remains after 10 weeks indicate Down syndrome
What does diagnostic testing involve?
Cells from samples can be cultured to obtain sufficient cells to produce a karyotype to diagnose a range of conditions
In deciding to proceed with these tests, the element of risk will be assessed as will the decisions the individuals concerned are likely to make if a test is positive
A karyotype shows an individuals chromosome arranged as homologous pairs
What are the two types of diagnostic testing?
Chorionic villus sampling
Amniocentesis
What is chorionic villus sampling(CVS)?
When a tiny sample of fetal cells from the placenta are taken from a tube inserted through the reproductive tract, and are then cultured and karyotype is produced
You can perform this earlier in pregnancy(8 weeks)
The karyotyping can be performed immediately
There’s an increased risk in miscarriage
Termination is less traumatic
What is amniocentesis?
A needle is used to gain a sample of amniotic fluid and the fetal cells(form amniotic sac) are cultured then karyotyped
Usually done at 14-16 weeks or later
Karyotyping takes 2 weeks
Decreased risk of miscarriage
Termination more traumatic
What is an allele, dominant, recessive, phenotype, genotype, heterozygous, homozygous
Allele- different forms of the same gene, inherited two alleles for each chromosome
Dominant- mask recessive allele, will always show
Recessive- only seen if both inherited alleles are recessive
Phenotype- physical characteristics/appearance
Genotype- different types of alleles an organism inherits, represented by 2 letters
Heterozygous- two different alleles of the same gene
Homozygous- two of the same alleles of the same gene
What is an autosome?
Any chromosome that’s not a sex chromosome
What are the four patterns of inheritance?
Autosomal recessive
Autosomal dominant
Autosomal incomplete dominance
Sex linked recessive trait
What is autosomal recessive?
Trait is expressed relatively rarely and may skip generations
Males and females equally affected
All sufferers are homozygous recessive, so non-sufferers will be homozygous dominant or heterozygous
Example- cystic fibrosis
What is autosomal dominant?
Appears in every generation
Each sufferer has affected parent
Males and female equally affected
All non sufferers are homozygous recessive
Example- huntingtons disease
What is autosomal incomplete dominance?
Fully expressed form of the disorder occurs relatively rarely, partially expressed form occurs more frequently
Males and females equally affected
Non sufferers are homozygous for one incompletely dominant allele(HH)
Sufferers of fully expressed form homozygous for the other incompletely dominant allele(SS)
Suffered of partly expressed form are heterozygous for the two alleles(HS)
Example- sickle cell disease
What is sex linked recessive?
More males are affected than females
No sons of an affected male show the trait
Grandsons of an affected male may show the trait
Sufferers of the trait are homozygous recessive(normally male XhY, rarely female XhXh)
Non sufferers of the trait are homozygous dominant (XHY or XHXH) or heterozygous carrier females (XHXh)
Example- duchenne muscular dystrophy
What is postnatal screening?
Diagnostic testing for phenylketonuria(PKU)
In PKU a substitution mutation means that the enzyme which converts phenylalanine to tyrosine is non functional
Individuals with high levels of phenylalanine are placed on a restricted diet
