Prenatal Testing - Invasive and Non-invasive Tests Flashcards
Why aren’t invasive tests part of routine procedure?
They come with risks to the mother and fetus, namely an increased risk of miscarriage
For which 3 reasons would a woman be offered an invasive prenatal test?
- Mother’s age is over 35
- Positive results from a screening test
- Family history of a genetic condition for which a test exists
Why would a woman be offered an invasive test because she is over 35?
Risk of aneuploidies and miscarriages increase with the age of the mother
What are the two invasive prenatal tests?
Chorionic villus sampling and amniocentesis
What is chorionic villus sampling?
A small amount of tissue is taken from the chorionic villus, which is genetically identical to the fetus
When does chorionic villus sampling become available?
At 11 weeks
What does chorionic villus sampling test for?
Trisomies and any other genetic conditions that we have a test for
What are the risks with chorionic villus sampling?
Elevated risk of miscarriage by 1-2%
What is amniocentesis?
A needle is inserted transabdominally into the uterus and a sample of amniotic fluid is taken, which will have some shed fetal cells
When does amniocentesis become available?
At 15 weeks
What does amniocentesis test for?
Trisomies and any other genetic conditions we have a test for
What are the risks with amniocentesis?
An elevated risk of miscarriage by 0.5%
Is amniocentesis or chorionic villus sampling used more often?
Amniocentesis. It has a lower risk of miscarriage
Are amniocentesis and chorionic villus sampling diagnostic or screening tests?
Diagnostic
What is non-invasive prenatal testing?
A blood sample from the mother is taken, which will contain fragments of fetal DNA which can be amplified and tested
