Antenatal and postnatal screening Flashcards
What does antenatal screening do
identifies the risk of a disorder so that further tests and a prenatal diagnosis can be offered
What are dating scans
given at 8-14 weeks which determines pregnancy stage and due date, are used with tests for marker chemicals which vary normally during pregnancy
What are anomaly scans
18-20 weeks may detect serious physical abnormalities in the fetus
Why are blood and urine tests carried out throughout pregnancy
to monitor the concentrations of marker chemicals
What can measuring a chemical at the wrong time lead to
False positive
What can an atypical chemical concentration lead to
diagnostic testing to determine if the fetus has a medical condition
What does CVS involve
obtaining CVS cells from the placenta
When would CVS be carried out
11-13 weeks
Why would a women be offered an CVS
if she has a higher risk result from a screening for downsyndrom
What are the risks of CVS
there is a 1 to 2 pecent risk of miscarriage
What is amniocentesis
amniocenteses cells are obtained from amniotic fluid
When is amniocentesis carried out
15-18 weeks
Why would a women be offered an amniocentesis
if she has a higher risk result from a screening for downs syndrom
What are the cells from CVS and amniocentesis used for
cells are cultures to produce a karyotype to diagnose a range of conditions
What is the risk of amniocentesis
1 percent risk of mmiscarriage
measuring the concentration of marker chemicals must be used with what
a dating scan
What are the advantages of amniocentesis and CVS 1
both are difinitive tests for trisomies
What occurs during PKU
a substitution mutation means that the enzyme which converts phenylalanine to tyrosine is non functional
What happens if PKU is not detected soon after birth
babys mental development is affected
What happens to individuals with high levels of phenlalanine
placed on a restricted diet
Describe the process by which a karyotype is produced from cells removed during CVS
cells are cultured to show the chromosomes
Explain why sex linked conditions occur more frequently in males than females
males need to inherit one affected allele but females would need to inherit 2
What term describes the testing of newborn babies for inherited disorders such as PKU
postnatal screening
