Amniocentesis and CVS

8/4/2019 Amniocentesis and CVS

1/38

Amniocentesis and CVS

Dr. Joseph Har-Toov

Lis Maternity Hospital

Tel-Aviv, Israel


2/38

Methods of chromosomal evaluation

Non invasive:

Fetal cells from maternal blood

preimplantation embryos (PGD)

Invasive: amniotic fluid (amniocentesis)

placenta (chorionic villus tissue)

Fetal blood


3/38

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


4/38

karyotypefish

PCR


5/38

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)


6/38

Amniocentesis

First introduced by Serr and Fuchs andRiis in the 1950s for fetal sexdetermination

Only at the late 70th a static ultrasoundwas used to locate the placenta andamniotic fluid pocket

Only In 1983, Jeanty reported atechnique of amniocentesis underultrasound vision


7/38

Mid Trimester Amniocentesis

Per coetaneous

20-23g needle

Ultrasound guided

Usually 20cc amniotic fluid

Results 2 to 3 weeks


8/38


9/38


10/38

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, previousvaginal bleeding

Placental perforation recent studies didntfind correlation


11/38

Complications

Leakage of amniotic fluid (better prognosisthan spontaneous leakage)

Amnionitis

Vaginal bleeding

Needle puncture of the fetus

Long term complications:

Respiratory distress?? Isoimmunization??


12/38

Amniocentesis and HIV positive

women

Increased rate of vertical transmission

Chemoprophylaxis previous toamniocentesis appears to be beneficial in

preventing vertical transmission


13/38

Multiple Gestation

Three methods:

Indigo carmine injection to the first sac

A single needle puncture sampling technique(Jeanty 1990)

Simultaneous visualization of two needles oneach side of the separating membrane (Bahado-Singh 1992)

Abortion risk probably higher

Detailed description of fetusposition and placental location


14/38

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 amnioticfluid leakage

laboratory failure op to 20%


15/38

Chorionic villus sampling

Was developed in the 80th

percutaneous transabdominal with 19-20gneedle


16/38

Chorionic villus sampling

Was developed in the 80th

percutaneous transabdominal

transvaginal

transcervical


17/38


18/38


19/38

15-30mg each aspiration 20mg ideal for cytogenetic testing

30-40mg for cytogenetic and other direct

molecular and biochemical tests


20/38

CVS results

Direct analysis examines the trophoblastcells of the placenta (very rapidly dividingcells) Results in few hours

greater vulnerability to mitotic error

Cultured analysis examines thefibroblast like cells of the villus stroma ormesenchymal core. Approximately 7-10 days

Accurately reflect the chromosomes of thefetus.


21/38

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%)


22/38

Risk of invasive procedure - CVS

Transabdominal CVS as safe as secondtrimester amniocentesis

Trans abdominal and transcervical CVS

are equally safe and efficacious, providedthat centers have expertise with bothapproaches

In approximately 35% of cases, clinical

circumstances will support one approachover the other

Limb reduction not after 9 weeks


23/38

mosaicism True chromosomal mosaicism is when two

or more abnormal cells lines are detectedin two or more culture flasks from the

same individual. Pseudomosaicism is a term used to

describe two abnormal cell lines that arefound in only one culture flask (not

reported to the patient)


24/38

mosaicism

Most often involving trisomic cell andnormal cells

1-2% of pregnancies undergoing CVS

0.1% of pregnancies undergoingamniocentesis

Clinical outcome of chromosomalmosaicism is strongly dependent on the

specific chromosome involved and thenumber of trisomic cells in both theplacenta and the fetus


25/38

Mosaicism (trisomic cells) in CVS

Option of an additional prenatal diagnosticprocedure (amniocentesis or fetal bloodsampling)


26/38

Mosaicism (trisomic cells) in CVS

Four possible conditions:

Mosaicism only in the placenta not affectingthe fetus or placental function.

Mosaicism only in the placenta not affectingthe fetus but alter placental function (IUGR)

Trisomy cells are both in the placenta and inthe fetus

Trisomy cells in the placenta and uniparentaldisomy in the fetus


27/38

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 withany prenatal procedure

Ultrasound is often the best judge of howa baby is developing
http://www.genome.gov/13514638


28/38

Uniparental Disomy

Arises when an individual inherits twocopies of a chromosome pair from oneparent and no copy from the other parent

Maternal UPD

two copies from the mother Paternal UPD two copies from the father


29/38

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 nocopies of the same chromosome, calledgamete complementation.


30/38

Trisomic rescue following an error in

meiosis

heterodisomy


31/38

Trisomic rescue followed an error in

meiosis II

isodisomy


32/38

UPD - health concerns in people

for two possible reasons:

Parental imprinting in the case ofheterodisomy and isodisomy

Unmasking of recessive conditions in some

cases of isodisomy


33/38

Clinical consequences of UPD

molecular UPD testing should beconsidered for certain chromosomes(including 6, 7, 11, 14, 15) that are

known to have adverse phenotypicimprinting effects.


34/38

Factors considered when trying to

predict the outcome of mosaicism the chromosome involved

A mosaic finding 18 or 21 is likely to haveworse implications

mosaic finding for trisomy 15 or 16 is likely tohave less implications (trisomy 15 or 16 cellscannot survive )


35/38


predict the outcome of mosaicism

The tissues affected and level oftrisomy in those tissues

The tissue affected cannot be evaluated

The level of trisomy can be only estimated


36/38



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

F id d h i


37/38



ultrasound findings presence/absence of uniparental

disomy number of previous case reports

known in the literature


38/38

Thank you

Amniocentesis and CVS

Documents

Transcript of Amniocentesis and CVS