CHORIONIC VILLUS SAMPLING

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CHORIONIC VILLUS SAMPLING

• BY
• Himani Patel

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What is chorionic villus sampling?

• CVS is the procedure of withdrawing a small
  portion of chorionic villus (placental tissue)
  from the pregnancy.
• It is best done between 10 and 12.5 wks of
  gestation and is performed under ultrasound
  guidance.
• CVS has been utilized as a genetic diagnostic
  method since the early 1980's.
• This tissue contains the same genetic material as
  the fetus.

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What kind of problems does the test detect?

• CVS detects chromosome abnormalities (i.e. Down
  syndrome, which causes mental retardation and
  health problems ) and genetic disorders (i.e.
  cystic fibrosis, a condition in which abnormal
  body secretions cause problems in the lungs and
  digestive system), Tay-Sac, which causes
  blindness, loss of function, and early death,
  Sickle cell anemia, a condition in which abnormal
  red blood cells interfere with many body
  processes
• CVS also provides access to DNA for paternity
  testing prior to delivery.
• The test does not detect spina bifida or other
  neural tube defects. A blood test known as
  alpha-fetoprotein can be done to screen for these
  disorders.

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Who should have CVS procedure?

• Women 35 years of age and older
• Parents who have had a child with Down syndrome
  or other chromosome abnormality
• Couples who are known carriers of a chromosome
  rearrangement
• Couples who have a family history of a genetic
  condition for which testing is available

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Who shouldnt have CVS procedure?

• CVS isnt recommended for women who
• In any woman who is further along in gestation
  than about 12 weeks counted from the first day of
  the last menstrual period.
• When there are certain vaginal infections
  present.
• Are carrying twins
• When the shape of the uterus is abnormal. This
  could be due to uterine fibroids or a bicornuate
  uterus.
• When heavy vaginal bleeding is occurring.

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What is the procedure for CVS?

• An ultrasound examination is performed first.
  Placental location is identified, fetal life is
  verified and a measurement of the fetus is taken
  to determine gestational age.
• Then, depending on the location of the placenta,
  the choice of method for CVS is made. The CVS is
  performed either through the cervix
  (transcervical CVS) or through the abdomen
  (transabdominal CVS).

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Ultrasound
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Placenta at back
Placenta at front (catheter used via cervix)
(Needle used through abdomen)
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Transcervical CVS

• For a transcervical CVS procedure
• The physician will insert an instrument called a
  speculum into your vagina to spread the walls of
  the vagina apart.
• Your vagina and cervix will be cleansed with an
  antiseptic solution.
• Using ultrasound, a thin tube will be guided
  through the cervix to the chorionic villi.
• Cells will be gently suctioned through the tube
  into a syringe. You may feel a twinge or slight
  cramping. More than one sample may be needed to
  obtain enough tissue for testing.
• The tube will then be removed.

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TransCervical CVS(Catheter used via cervix)
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(catheter used via cervix)

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TransCervical CVS
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Transabdominal CVS
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Transabdominal CVS

• For a transabdominal CVS procedure
• For an abdominal CVS, your abdomen will be
  cleansed with an antiseptic.
• The physician may inject a local anesthetic to
  numb the skin. If a local anesthetic is used, you
  will feel a needle stick when the anesthetic is
  injected. This may cause a brief stinging
  sensation.
• Ultrasound will be used to help guide a long,
  thin, hollow needle through your abdomen and into
  the uterus and placenta. This may be slightly
  painful, and you may feel a cramp as the needle
  enters the uterus.
• Cells will be gently suctioned into a syringe.
  More than one sample may be needed to obtain
  enough tissue for testing.
• The needle will then be removed. An adhesive
  bandage will be placed over the abdominal needle
  insertion site.

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Transabdomen CVS(Needle used through abdomen)
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Transabdominal CVS
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Transabdominal CVS
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What are the benefit of CVS?

• The benefits of CVS include the following
• early diagnosis of a chromosomal abnormality
• early diagnosis of certain genetic defects.

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What are the risks of CVS?

• The risks of CVS include the following
• miscarriage(1/2 1) CVS has a similar or
  slightly higher rate of pregnancy loss compared
  to amniocentesis.
• infectionCVS is an invasive procedure and may
  cause infection.
• limb defectsSome reports show that babies born
  after CVS may have an increased rate of limb
  (arm, leg, or finger) defects. Other studies have
  refused this finding (the risk for a limb anomaly
  after CVS is approx. 1 in 3,000, which is similar
  to that seen in the general population).

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 How do I decide whether to have CVS or wait for
an amnio?

• The CVS may be a better choice if You're at risk
  for having a baby with a chromosomal problem and
  you want to know your baby's condition during
  your first trimester, either so that you can
  terminate the pregnancy early if necessary or
  just cut down on worrying time. (If you wait for
  the amnio at 15 weeks, then 17 weeks is the
  soonest you'd be able to know the situation or
  end the pregnancy.)
• Amniocentesis may be a better choice if You
  decide you want to wait for the results of a
  multiple marker screening (usually done between
  15 and 20 weeks), before subjecting yourself to a
  more invasive test. (The CVS must be done by 12
  weeks to be effective.)

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What happens after the test?

• Generally women are advised to rest for a few
  hours after CVS.
• abstain from strenuous physical activity, sex,
  and exercise for three days.
• Slight bleeding cramping is common and may last
  up to a week, particularly if you had the
  transcervical procedure.
• If you notice fluid leaking from your vagina or
  have a fever, call your doctor or midwife
  immediately.
• The results from CVS are usually available within
  a few days two weeks, depending on cell growth.

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References

• http//www.modimes.org/professionals/681_1165.asp
• http//www.babycenter.com/refcap/pregnancy/prenata
  lhealth/328.html
• http//www.peacehealth.org/kbase/topic/medtest/hw4
  104/descrip.htm
• http//www.cpdx.com/cpdx/cvs.htm 
• http//www.pmhs.org/crs/wha/crs/cvs.htm
• http//www.amnionet.com/eldorl.gif 
• http//www.amnionet.com/rindl.gif