What is the difference between screening tests and diabnostic tests
screening tests looks to identify babies general risk in a population with a higher risk of birth defects.
Diagnostic tests look at wether that particular inidividual has been affected.
what are we looking for in diagnostic tests
- neural tube defects
- aneuploidies
- mutated genes or structural errors in chromosomes
what type of test would be done from maternal serum and maternal blood
screeening
what type of testing woulf be done from amniotic fluid, chorionic villi, and fetal blood
Diagnostic
what is a ultra sound
uses sound-wave reflections to make a highly-detailed image of tissue interfaces.
when are the two ultrasound images taken
1st scan in 1st trimester 11-14 weeks
2nd scan in 2nd trimester at 18-22 weeks
What is scaned in the 1st ultrasound scan
- confirms gestinal age and number of fetuses
- nuchal translucency
what is nuchal translucency
a screening for aneuploidy by measring the thickenss of fluid compartment in the embryo’s neck - used along the maternal serum blood testing to enhance results. Trisomy 18 and 21
what is imaged for in the 2nd scan for in ultrasound
detailed anatomical survey to identify half of structural malformations - can be diagnostic for some
what is maternal serum alpha-fetoprotien and where can it be detected.
it is secreted by fetal liver and excreted in fetal urine. crosses the placenta, detected in maternal serum.
when is it screened and waht could cause high liveles.
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what is AFP part of and what does that also measure.
part of the maternal serum quadruple screen (MSS)
- also measures 3 other molecules: HCG, estroul, inihibin - A
What hapenes with low AFP, abnormal hcG and Estaroil
aneuploidy
what is the risk with diagnostic testss and when is it recomended
risk of miscarage since it is invasive, only recomended with advanced maternal age or familyt history of birth defects
what are the diagnostic tests for and what are the types of twst
test for chromosommal abnormalities, chorionic villus sampling btw 10-12 weeks
amniocentesis btw 14-16 weeks
fetal blood sample from umbilical vein after 18 weeks.
what can amniocentesis measure and analyse
AFP levels, fluid composistion analyzis, cells karyotype, sex determination, biochemical and recombinant studies, cell culture to chromosomal analysis, analysis using recombinant DNA methods.
what to do if an anomaly is detected
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