Transcript Amniocentesis and CVS

Amniocentesis and CVS
Dr. Joseph Har-Toov
Lis Maternity Hospital
Tel-Aviv, Israel
Methods of chromosomal evaluation
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Non invasive:
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Fetal cells from maternal blood
preimplantation embryos (PGD)
Invasive:
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amniotic fluid (amniocentesis)
placenta (chorionic villus tissue)
Fetal blood
Invasive techniques
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Amniocentesis:
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Chorionic villus sampling (CVS)
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Late – second trimester after 15 weeks
Early – earlier than 15 weeks
Abdominal
Trans cervical
Trans vaginal
Fetal blood sampling
karyotype
fish
PCR
What can be evaluated?
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Chromosomal aberrations:
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Trisomy,
Monosomy,
Polyploidy,
Marker chromosome,
Deletion, duplication, inversion, translocation,
ring chromosome .
Genetic aberrations (DNA)
 Infectious disease
 Biochemical markers (AFP)
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Amniocentesis
First introduced by Serr and Fuchs and
Riis in the 1950s for fetal sex
determination
 Only at the late 70th a static ultrasound
was used to locate the placenta and
amniotic fluid pocket
 Only In 1983, Jeanty reported a
technique of amniocentesis ’’under
ultrasound vision’’
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Mid Trimester Amniocentesis
Per coetaneous
 20-23g needle
 Ultrasound guided
 Usually 20cc amniotic fluid
 Results – 2 to 3 weeks
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complications
Pregnancy loss 0.3-1.0%.
 Increase risk:
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Needle larger than 18g
Multiple needle insertion
Discoloration of the fluid
High AFP, multiple late abortions, previous
vaginal bleeding
Placental perforation – recent studies didn’t
find correlation
Complications
Leakage of amniotic fluid (better prognosis
than spontaneous leakage)
 Amnionitis
 Vaginal bleeding
 Needle puncture of the fetus
 Long term complications:
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Respiratory distress??
Isoimmunization??
Amniocentesis and HIV positive
women
Increased rate of vertical transmission
 Chemoprophylaxis previous to
amniocentesis appears to be beneficial in
preventing vertical transmission
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Multiple Gestation
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Three methods:
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Indigo carmine injection to the first sac
A single needle puncture sampling technique
(Jeanty 1990)
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Simultaneous visualization of two needles on
each side of the separating membrane (BahadoSingh 1992)
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Abortion risk – probably higher
Detailed description of fetus
position and placental location
Early Amniocentesis: 9-14 weeks
Introduced at late 80th
 10-14 weeks gestation
 Only the amniotic (inner) sac should be
aspirated
 Approximately 1 cc for gestational age
 Higher rate of pregnancy loss, talipes
equinovarus, and post procedural amniotic
fluid leakage
 laboratory failure op to 20%
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Chorionic villus sampling
Was developed in the 80th
 percutaneous transabdominal with 19-20g
needle
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Chorionic villus sampling
Was developed in the 80th
 percutaneous transabdominal
 transvaginal
 transcervical
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15-30mg each aspiration
 20mg ideal for cytogenetic testing
 30-40mg for cytogenetic and other direct
molecular and biochemical tests
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CVS results
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Direct analysis examines the trophoblast
cells of the placenta (very rapidly dividing
cells)
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Results in few hours
greater vulnerability to mitotic error
Cultured analysis examines the
fibroblast like cells of the villus stroma or
mesenchymal core.
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Approximately 7-10 days
Accurately reflect the chromosomes of the
fetus.
Risk of invasive procedure
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Early amniocentesis:
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High
High
High
High
pregnancy loss
fetal malformations
rate of multiple needle insertions (4.7%)
rate laboratory failures (1.8%)
Late amniocentesis:
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“Low” pregnancy loss (0.3-1%)
Low rate of multiple needle insertions (1.7%)
Low rate laboratory failures (0.2%)
Risk of invasive procedure - CVS
Transabdominal CVS as safe as second
trimester amniocentesis
 Trans abdominal and transcervical CVS are
equally safe and efficacious, provided that
centers have expertise with both
approaches
 In approximately 3–5% of cases, clinical
circumstances will support one approach
over the other
 Limb reduction – not after 9 weeks
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mosaicism
True chromosomal mosaicism is when two
or more abnormal cells lines are detected
in two or more culture flasks from the
same individual.
 Pseudomosaicism is a term used to
describe two abnormal cell lines that are
found in only one culture flask (not
reported to the patient)
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mosaicism
Most often involving trisomic cell and
normal cells
 1-2% of pregnancies undergoing CVS
 0.1% of pregnancies undergoing
amniocentesis
 Clinical outcome of chromosomal
mosaicism is strongly dependent on the
specific chromosome involved and the
number of trisomic cells in both the
placenta and the fetus
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Mosaicism (trisomic cells) in CVS
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Option of an additional prenatal diagnostic
procedure (amniocentesis or fetal blood
sampling)
Mosaicism (trisomic cells) in CVS
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Four possible conditions:
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Mosaicism only in the placenta not affecting
the fetus or placental function.
Mosaicism only in the placenta not affecting
the fetus but alter placental function (IUGR)
Trisomy cells are both in the placenta and in
the fetus
Trisomy cells in the placenta and uniparental
disomy in the fetus
Mosaicism (trisomic cells) in
amniotic fluid
Probably there are trisomic cells in the
fetus
 The true level and distribution of trisomic
cells cannot be accurately assessed with
any prenatal procedure
 Ultrasound is often the best judge of how
a baby is developing
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Uniparental Disomy
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Arises when an individual inherits two
copies of a chromosome pair from one
parent and no copy from the other parent
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Maternal UPD – two copies from the mother
Paternal UPD – two copies from the father
How does UPD happen?
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Loss of a chromosome from a trisomic
zygote, "trisomic rescue"
Duplication of a chromosome from a
monosomic zygote, "monosomic rescue"
Fertilization of a gamete with two copies
of a chromosome by a gamete with no
copies of the same chromosome, called
gamete complementation.
Trisomic rescue following an error in
meiosis
heterodisomy
Trisomic rescue followed an error in
meiosis II
isodisomy
UPD - health concerns in people
for two possible reasons:
Parental imprinting in the case of
heterodisomy and isodisomy
 Unmasking of recessive conditions in some
cases of isodisomy
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Clinical consequences of UPD
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molecular UPD testing should be
considered for certain chromosomes
(including 6, 7, 11, 14, 15) that are
known to have adverse phenotypic
imprinting effects.
Factors considered when trying to
predict the outcome of mosaicism
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the chromosome involved
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A mosaic finding 18 or 21 is likely to have
worse implications
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mosaic finding for trisomy 15 or 16 is likely to
have less implications (trisomy 15 or 16 cells
cannot survive )
Factors considered when trying to
predict the outcome of mosaicism
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The tissues affected and level of
trisomy in those tissues
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The tissue affected cannot be evaluated
The level of trisomy can be only estimated
Factors considered when trying to
predict the outcome of mosaicism
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method of ascertainment
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CVS shows that the placenta is affected
Amniotic fluid suggests that at least one fetal
tissue may be affected
Fetal blood sampling confirms the diagnosis of
chromosomal mosaicism
Factors considered when trying to
predict the outcome of mosaicism
ultrasound findings
 presence/absence of uniparental
disomy
 number of previous case reports
known in the literature
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Thank you