37233502 amniocentesis-and-cvs
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Transcript of 37233502 amniocentesis-and-cvs
Amniocentesis and CVS
Methods of chromosomal evaluation Non invasive:
Fetal cells from maternal blood preimplantation embryos (PGD)
Invasive: amniotic fluid (amniocentesis) placenta (chorionic villus tissue) Fetal blood
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
karyotypefish
PCR
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)
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’’
Mid Trimester Amniocentesis Per coetaneous 20-23g needle Ultrasound guided Usually 20cc amniotic fluid Results – 2 to 3 weeks
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 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:
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
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
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%
Chorionic villus sampling Was developed in the 80th
percutaneous transabdominal with 19-20g needle
Chorionic villus sampling Was developed in the 80th
percutaneous transabdominal transvaginal transcervical
15-30mg each aspiration 20mg ideal for cytogenetic testing 30-40mg for cytogenetic and other direct
molecular and biochemical tests
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.
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%)
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
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)
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
Mosaicism (trisomic cells) in CVS
Option of an additional prenatal diagnostic procedure (amniocentesis or fetal blood sampling)
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
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
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
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.
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
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.
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 )
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
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
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
Thank you