An invasive procedure of taking out chorionic tissue for prenatal diagnosis.

1. Chorion Biopsy
Dr Shreshtha Aggarwal
Fetal Medicine Consultant
SFMC
Bathinda, Punjab

2. Definition
Chorion Biopsy or more popularly known as Chorionic
villus sampling (CVS): an invasive procedure
performed for first-trimester prenatal diagnosis.
CVS is typically performed between 70 and 91 days
after the LMP. In the procedure, tissue is withdrawn
from the villi (vascular fingers) of the chorion, a part
of the placenta, and examined.

3. Embryology of Chorion
FrondosumBefore 9 weeks, chorionic villi cover the
entire outer surface of the gestational sac.
As growth continues, the developing sac
begins to fill the uterine cavity, and most
villi regress except at the implantation site,
where they are associated with the
decidua basalis . Villi in this area rapidly
proliferate to form the chorion frondosum
Between 9 and 12 weeks of gestation, the
villi float freely within the blood of the
intervillus space and are only loosely
anchored to the underlying decidua
basalis.

4. Chorionic villi are fetal in origin,
 Appropriate and useful source of tissue for the
evaluation of fetal genetic disease.
Their cytogenetic, molecular, and biochemical properties
reflect those of the fetus.
The villi are partly composed of cytotrophoblast cells,
which are an actively dividing source of spontaneous
mitoses that can be used to obtain a rapid chromosomal
analysis

5. Advantages of CVS?
Yield of cells and DNA from CVS is much greater
than 20ml of amniotic fluid
With shift towards first trimester screen
procedure of choice
Biochemical or DNA analysis can usually be carried
out directly on villi obviating the need and delay of a
cell culture as required after amniocentesis.

6. Indications
CVS can be done for all indications of AC
Cytogenetic: Karyotype/ Single gene disorders
Metabolic: in born errors of metabolism
Molecular: hemoglobinopathies, hemophilia,

7. Indications
Previous child with nondisjunctional chromosome
abnormality
Parent is carrier of balanced translocation or other
chromosome disorder
Both parents are carriers of autosomal recessive disease
Women who are carriers of a X-linked disease
Positive first-trimester screen for trisomy 21 or 18

8. Myth!!!!!
CVS is technically more difficult and riskier as
compared to amniocentesis!!!
 Cochrane review (2003)
Total pregnancy loss after TA-CVS is comparable to 2nd trimester
amnio (OR 0.9; 95% CI 0.66-1.23). Higher with TC-CVS ( OR 1.4)
 Danish national registry, cohort of over 65,000
miscarriage rates < 24 weeks for amnio vs CVS (1,4 vs 1.9%), overall
0.5-1%
 Mujezinovic and Alfirevic, 2007
CVS:Within 2weeks 0.7%, < 24 weeks, 1.3%, Total 2%
Amnio 0.6 % fetal loss within 2wks, 0.9% <24wk, 1.9% total

9. Sampling Technique
Trans Abdominal
Trans Cervical
Though both are equally safe and either can be done in
almost 95-97 %, trans abdominal is a preferred method
and is done by most of the centres

10. Pre procedure
Ultrasound : placental site, number of fetuses,
viability, congenital abnormality, access path
Maternal ABO & Rh grp, Hb
Informed, written consent

11. Trans Abdominal CVS-
Technique
Maternal Abdomen is painted and draped
Gauge 18-20 disposable spinal needle of adequate length (7.5-15mm)
used
The needle passed through anterior abdominal wall into the substance of
the chorion frondosum under continuous ultrasound guidance by freehand
/ needle guide technique.
The stylet is withdrawn and 20ml syringe attached.
Gentle up & down movements with continuous negative pressure are
made taking care to avoid puncturing fetal aspect of amniotic membrane by
U/S control with continuous needle tip visualization.

12. The Procedure

13. The tissue is then transferred to the culture
medium containing tubes or petri dish and
examined for adequacy of CV before the needle is
withdrawn.
The chorionic villi appear as free-floating,
white structures with fluffy, filiforme branches.
Contaminating decidua tissue has a more
amorphous appearance and lacks distinct branches

14. Transcervical CVS-
Technique
1.5mm cannula made of plastic with metal obturator
Distal 3-5 cm obturator slightly curved
Under aseptic conditions, cannula passed through Cx till internal
OS reached (cervix usually held with tenaculum)
Cannuala tip visualized under U/S guidance is advanced & guided
into the substance of chorion frondosum
Cannula placed parallel to axis of developing placenta & advanced
almost to distal end

16. Post Procedure Care
Antibiotics
To expect mild spotting for 3-5 days.
To expect slight pain for 1-2 days.
Restricted activity 1-2 days.
Abstinence - 2 weeks
Follow up ultrasound after 2 weeks

17. Complications
Bleeding
Rupture of membranes
Elevated MSAFP
Chorio- amnionitis
Rh Isoimmunisation
Pregnancy Loss
Fetal Malformations -oro mandibular limb
hypogenesis syndrome,terminal
transverse limb reduction defect

18. Lab Aspects of CVS
Tests done
FISH
Karyotype
Molecular
Metabolic

19. Pictures
Courtesy:
Genecare
Genetic Lab,
Surat

20. Limitations
Maternal Cell Contamination
Confined Placental Mosaicism

21. To Conclude
1. Chorionic villus sampling has a low complication rate
comparable to mid-trimester amniocentesis in
experienced hands.
2. CVS is the preferable method of fetal aneuploidy
testing in the first trimester
The aim of Prenatal diagnosis employing any technique
is not to generate perfect babies, But it is to let parents
know about the health of their unborn child to help
them make informed decisions in context of their value
system

22. Thank You!
There are no perfect human
specimens, we are all genetically
flawed – Francis Collins