Amniocentesis and CVS GTG

Question 1

What does CVS sample?

Answer 1

Placental villi

Question 2

When is CVS usually performed?
What is the maximum gestation CVS can be performed until?

Answer 2

11-13+6
Max 14+6

CVS should not be performed before 10 weeks.

Question 3

When is amniocentesis performed?

Answer 3

From 15 weeks

Normally 16-22 weeks, but can be performed later

Question 4

What do QF-PCR and FISH test for? How long do results take?

Answer 4

Downs/Edwards and Pataus
Rapid test 3 days

Question 5

What other tests can be performed following CVS?

Answer 5

Full karyoptye

Microarray CGH - look for deletions/duplications - results can take 2 weeks

Question 6

Risk of miscarriage following CVS/amniocentesis

Answer 6

1 in 200 (0.5%), often within 72 hours.

Question 7

How many CVS should an obstetrician do a year to minimise risk miscarriage according to RCOG?

Answer 7

20 per year

Question 8

If twin pregnancy what is risk of miscarriage/amniocentesis?

Answer 8

2%

Question 9

What is the risk of placental mosaicism following CVS?

Answer 9

1-2%

Question 10

In CVS if QF-PCR shows chromosomal anomaly but no structural abnormally, what should you do?

Answer 10

Await full karyotype before offering TOP.

If structural abnormality, reasonable to offer TOP

Question 11

Risk of repeat procedure for both CVS and amnio?

Answer 11

Up to 6%

Question 12

Risk maternal cell contamination for both CVS and Amnio?

Answer 12

1-2%

Question 13

Risk rapid test failure for both CVS and amnio?

Answer 13

0.5-1%

Question 14

Risk of blood stained sample with amnio

Answer 14

0.8%

Question 15

Risk of severe infection/fetal injury/maternal visceral injury

Answer 15

Rare

Question 16

Why should amniocentesis not be performed before 15 weeks?

Answer 16

Increased risk of pregnancy loss and talipes equinovarus

Question 17

Why should CVS not be performed under 10 weeks?

11 weeks?

Answer 17

Possible oromandibular and limb defects

Before 11 - more technically challenging

Question 18

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

Answer 18

3-4%

10% culture failure

Question 19

What is the risk of cell culture failure for CVS and amnio

Answer 19

0.5-1%

Question 20

What bloods should be reviewed before performing invasive testing?

Answer 20

Screening results for HIV and blood borne viruses

Delay test if HIV test not done

Question 21

Risk of transmission of Hepatitis B is low if viral low is below what value?

Answer 21

6.99 log10 copies/ml

Question 22

Which form of invasive testing has more extensive testing for HIV mothers?

Answer 22

Amniocentesis

Question 23

What patient website is helpful for understanding these tests and their results?

Answer 23

Antenatal results and choices (ARC)

Question 24

When Is the combined screening performed?

Answer 24

11-14 weeks

Question 25

When is the quadruple testing performed?

Answer 25

14-20 weeks

Question 26

When can NIPT be performed

Answer 26

From 10 weeks