Amniocentesis and CVS GTG Flashcards
What does CVS sample?
Placental villi
When is CVS usually performed?
What is the maximum gestation CVS can be performed until?
11-13+6
Max 14+6
CVS should not be performed before 10 weeks.
When is amniocentesis performed?
From 15 weeks
Normally 16-22 weeks, but can be performed later
What do QF-PCR and FISH test for? How long do results take?
Downs/Edwards and Pataus
Rapid test 3 days
What other tests can be performed following CVS?
Full karyoptye
Microarray CGH - look for deletions/duplications - results can take 2 weeks
Risk of miscarriage following CVS/amniocentesis
1 in 200 (0.5%), often within 72 hours.
How many CVS should an obstetrician do a year to minimise risk miscarriage according to RCOG?
20 per year
If twin pregnancy what is risk of miscarriage/amniocentesis?
2%
What is the risk of placental mosaicism following CVS?
1-2%
In CVS if QF-PCR shows chromosomal anomaly but no structural abnormally, what should you do?
Await full karyotype before offering TOP.
If structural abnormality, reasonable to offer TOP
Risk of repeat procedure for both CVS and amnio?
Up to 6%
Risk maternal cell contamination for both CVS and Amnio?
1-2%
Risk rapid test failure for both CVS and amnio?
0.5-1%
Risk of blood stained sample with amnio
0.8%
Risk of severe infection/fetal injury/maternal visceral injury
Rare
Why should amniocentesis not be performed before 15 weeks?
Increased risk of pregnancy loss and talipes equinovarus
Why should CVS not be performed under 10 weeks?
11 weeks?
Possible oromandibular and limb defects
Before 11 - more technically challenging
If amniocentesis is performed in the 3rd trimester,
i) what is the chance of preterm birth <34/40
ii) what is the risk of cell culture failure
3-4%
10% culture failure
What is the risk of cell culture failure for CVS and amnio
0.5-1%
What bloods should be reviewed before performing invasive testing?
Screening results for HIV and blood borne viruses
Delay test if HIV test not done
Risk of transmission of Hepatitis B is low if viral low is below what value?
6.99 log10 copies/ml
Which form of invasive testing has more extensive testing for HIV mothers?
Amniocentesis
What patient website is helpful for understanding these tests and their results?
Antenatal results and choices (ARC)
When Is the combined screening performed?
11-14 weeks
When is the quadruple testing performed?
14-20 weeks
When can NIPT be performed
From 10 weeks
