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CVS results ... Trans abdominal and transcervical CVS ar

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CVS results ... Trans abdominal and transcervical CVS are equally safe and efficacious, provided ... CVS shows that the placenta is affected ... – PowerPoint PPT presentation

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Title: CVS results ... Trans abdominal and transcervical CVS ar


1
Amniocentesis and CVS
  • Dr. Joseph Har-Toov
  • Lis Maternity Hospital
  • Tel-Aviv, Israel

2
Methods of chromosomal evaluation
  • Non invasive
  • Fetal cells from maternal blood
  • preimplantation embryos (PGD)
  • Invasive
  • amniotic fluid (amniocentesis)
  • placenta (chorionic villus tissue)
  • Fetal blood

3
Invasive techniques
  • Amniocentesis
  • Late second trimester after 15 weeks
  • Early earlier than 15 weeks
  • Chorionic villus sampling (CVS)
  • Abdominal
  • Trans cervical
  • Trans vaginal
  • Fetal blood sampling

4
karyotype
fish
PCR
5
What can be evaluated?
  • Chromosomal aberrations
  • Trisomy,
  • Monosomy,
  • Polyploidy,
  • Marker chromosome,
  • Deletion, duplication, inversion, translocation,
    ring chromosome .
  • Genetic aberrations (DNA)
  • Infectious disease
  • Biochemical markers (AFP)

6
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

7
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
  • Needle larger than 18g
  • Multiple needle insertion
  • Discoloration of the fluid
  • High AFP, multiple late abortions, previous
    vaginal bleeding
  • Placental perforation recent studies didnt
    find correlation

11
Complications
  • Leakage of amniotic fluid (better prognosis than
    spontaneous leakage)
  • Amnionitis
  • Vaginal bleeding
  • Needle puncture of the fetus
  • Long term complications
  • Respiratory distress??
  • Isoimmunization??

12
Amniocentesis and HIV positive women
  • Increased rate of vertical transmission
  • Chemoprophylaxis previous to amniocentesis
    appears to be beneficial in preventing vertical
    transmission

13
Multiple Gestation
  • Three methods
  • Indigo carmine injection to the first sac
  • A single needle puncture sampling technique
    (Jeanty 1990)
  • Simultaneous visualization of two needles on each
    side of the separating membrane (Bahado-Singh
    1992)
  • Abortion risk probably higher
  • Detailed description of fetus
    position and placental location

14
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

15
Chorionic villus sampling
  • Was developed in the 80th
  • percutaneous transabdominal with 19-20g needle

16
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

20
CVS results
  • Direct analysis examines the trophoblast cells of
    the placenta (very rapidly dividing cells)
  • Results in few hours
  • greater vulnerability to mitotic error
  • Cultured analysis examines the fibroblast like
    cells of the villus stroma or mesenchymal core.
  • Approximately 7-10 days
  • Accurately reflect the chromosomes of the fetus. 

21
Risk of invasive procedure
  • Early amniocentesis
  • High pregnancy loss
  • High fetal malformations
  • High rate of multiple needle insertions (4.7)
  • High rate laboratory failures (1.8)
  • Late amniocentesis
  • Low pregnancy loss (0.3-1)
  • Low rate of multiple needle insertions (1.7)
  • Low rate laboratory failures (0.2)

22
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 35 of cases, clinical
    circumstances will support one approach over the
    other
  • Limb reduction not after 9 weeks

23
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)

24
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

25
Mosaicism (trisomic cells) in CVS
  • Option of an additional prenatal diagnostic
    procedure (amniocentesis or fetal blood sampling)

26
Mosaicism (trisomic cells) in CVS
  • Four possible conditions
  • 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

27
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

28
Uniparental Disomy
  • Arises when an individual inherits two copies of
    a chromosome pair from one parent and no copy
    from the other parent
  • Maternal UPD two copies from the mother
  • Paternal UPD two copies from the father

29
How does UPD happen?
  • 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.

30
Trisomic rescue following an error in meiosis
heterodisomy
31
Trisomic rescue followed an error in meiosis II
isodisomy
32
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

33
Clinical consequences of UPD
  • molecular UPD testing should be considered for
    certain chromosomes (including 6, 7, 11, 14, 15)
    that are known to have adverse phenotypic
    imprinting effects. 

34
Factors considered when trying to predict the
outcome of mosaicism
  • the chromosome involved
  • A mosaic finding 18 or 21 is likely to have worse
    implications
  • mosaic finding for trisomy 15 or 16 is likely to
    have less implications (trisomy 15 or 16 cells
    cannot survive )

35
Factors considered when trying to predict the
outcome of mosaicism
  • The tissues affected and level of trisomy in
    those tissues
  • The tissue affected cannot be evaluated
  • The level of trisomy can be only estimated   

36
Factors considered when trying to predict the
outcome of mosaicism
  • method of ascertainment  
  • 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

37
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  

38
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