Prenatal Diagnosis Flashcards
Non invasive tests
- Ultrasound Scan
- Maternal Blood tests
Invasive tests
Chorion Villus Biopsy (CVB)
Amniocentesis
Cordocentesis
Chorion Villus Biopsy is used to …
check karyotype of fetus
Chorion Villus Biopsy can be used to diagnose
- Down Syndrome
2.Cystic Fibrosis - Thalassemia
Amniocentesis used to diagnose
1.Down Syndrome
2. Cystic Fibrosis
3.Thalassemia
Cordocentisis used to diagnose
Alloimmune thrombocytopenia
An U/S scan followed by an invasive procedure can be used for what fetal issues?
- Congenital diaphragmatic hernia
2.Ventriculomegaly
3.Exomphalos - Dued. Atresia
What is done in a Chorion Villus Biopsy?
Sample of fetal trophoblastic cells is taken.
Method of Chorion Villus Sampling
1.pass needle through abdominal wall into placenta under U/S guide
2. Pass catheter/biopsy forceps through cervix into placenta w/ U/S guide.
Why should an U/S scan be done before a CVB procedure?
- Ensure Viability
- Confirm Single Preg.
- Confirm G. Age (+10weeks)
4.Localize Placenta
What is an Amniocentesis Procedure?
Procedure done to take sample of amniotic fluid containing cells.
When can an Amniocentesis procedure be done?
+15wks
Method of Amniocentesis
Needle passed through abdominal wall into amniotic cavity under U/S guidance and fluid is aspirated (15-20mL)
Advantage and Disadvantage of CVB over Amniocentesis
CVB can be done earlier than amniocentesis.
CVB has higher miscarriage risk (2%)
What is a Cordocentesis procedure?
Acquire fetal blood sample for rapid full culture of karyotype.
Most common indication for cordocentesis
Check for fetal platelet count in suspected alloimmune thrombocytopenia.
Method of Cordocentesis
Done +20wks.
Needle passed into Umbilical cord where it enters placenta under U/S guidance.
The most common reason for prenatal invasive tests is…
Down Syndrome
Test used for Down Syndrome and when
Combined test @ 11-14wks
Combined Test
@11-14wks
1. U/S scan to measure nuchal lucency
2. Maternal Blood test for HCG and PAPP-A (preg. associated plasma protein-A)
Define Nuchal Lucency
Thickness of pad of skin in neck region of fetus
Risk of down syndrome is based on
maternal age
combined test results
