41. Prenatal genetic counseling (chorionic villus sampling, amniocentesis, cordocentesis) Flashcards
what does prenatal diagnosis include?
all diagnostic and screening methods that can detect or exclude morphological, structural, functional, chromosomal, and molecular defects of the fetus
Non-invasive testing
US
MRI
Non-invasive prenatal testing (NIPT)
Triple/Quad biochemical screening
Invasive testing
- Amniocentesis (AC)
- Chorionic villous sampling (CVS)
- Percutaneous umbilical blood sampling (PUBS)
- Fetal tissue sampling
what is Amniocentesis?
US-guided, amniotic fluid sampling by needle aspiration (approx. 10 mL fluid)
when is amniocentesis performed?
16-20 gestational w’
Rate of pregnancy loss with amniocentesis?
0.5-1%
Rate of pregnancy loss with Chorionic villous sampling (CVS)?
2-3%
what is Chorionic villous sampling (CVS)?
US-guided, chorionic villous sampling by catheter or needle at 10-12 gestational w’
what risk is there in CVS?
Risk of vascular limb malformation (1:3000)
what is Cordocentesis – Percutaneous umbilical blood sampling (PUBS) used for?
- diagnostic test-examine fetal blood from the umbilical cord. Allows for rapid diagnosis because of the high number of nucleated cells (WBCs) collected which require no culturing.
- therapeutic- for fetal transfusion (ex. fetal anemia 2° to Rh incompatibility).
what is measured in PUBS?
The percutaneous umbilical approach also allows for the measurement of fetal hemoglobin, hematocrit, blood gases, pH, bilirubin, and antibodies.
Positive NIPT results must be confirmed by?
a diagnostic test (amniocentesis or CVS)
what is Non-invasive prenatal testing (NIPT)?
Cell-free fetal DNA collected from maternal plasma is used for genetic analysis. it accounts for up to 10% of total maternal plasma-free DNA at the end of the 1st trimester.
when is the biochemical screening performed?
during the 2nd trimester.
what is biochemical screening (Triple screen test vs. Quad screen test) used for?
classify the patient as either high-risk or low-risk for chromosomal abnormalities, and potentially neural tube defects (NTDs).
