Chorionic Villis Sampling (CVS)

Last updated 20.09.12

 

Index

 

Rationale

-  Antenatal genetic test on placental sample (chorionic villi)

-  Looks for Down Syndrome, CF

 

Chorionic Villi

 

Indications

-  Offered to women

-  > 37 years

-  Indications of Down Syndrome from blood tests & nuchal transluceny

-  W previous pregnancies effected by genetic abnormalities (CF, Down Syndrome..)

-  Family Hx of hereditary disorders (CF, thalassaemia..)

 

Features

-  Performed between weeks 10 -14

-  Available earlier than amniocentesis but higher risk

-  1% risk of miscarriage

-  May cause leakage of fluid: oligohydramnios

 

Procedure

-  Ultrasound performed 1st

-  Confirm gestational age & placental site

-  Best performed w full bladder

-  Can be performed transabdominally or transvaginally

-  Expose abdomen

-  Clean abdomen w antiseptic (betadine)

-  Inject site w local anaeshtetic (lidnocaine)

-  Wait for anaesthetic to take effect

-  Inesert needle into placenta w ultrasound guidance

-  Aspirate tissue into syringe

-  Empty contents into container w ..

-  Examine for adequate sample

-  Repeat ultrasound to confirm foetal stability

-  Patch CVS site w dressing

 

CVS

Results

-  Mosaicism may be present in placental cells (1-2%)

-  Result is indeterminate

-  Requires repeat for confirmation

-  Maternal cell contamination

-  Gender

-  Cannot detect all birth defects