5 What can be evaluated? Chromosomal aberrations: Trisomy,Monosomy,Polyploidy,Marker chromosome,Deletion, duplication, inversion, translocation, ring chromosome .Genetic aberrations (DNA)Infectious diseaseBiochemical markers (AFP)
6 AmniocentesisFirst introduced by Serr and Fuchs and Riis in the 1950s for fetal sex determinationOnly at the late 70th a static ultrasound was used to locate the placenta and amniotic fluid pocketOnly In 1983, Jeanty reported a technique of amniocentesis ’’under ultrasound vision’’
7 Mid Trimester Amniocentesis Per coetaneous20-23g needleUltrasound guidedUsually 20cc amniotic fluidResults – 2 to 3 weeks
10 complications Pregnancy loss 0.3-1.0%. Increase risk: Needle larger than 18gMultiple needle insertionDiscoloration of the fluidHigh AFP, multiple late abortions, previous vaginal bleedingPlacental perforation – recent studies didn’t find correlation
11 ComplicationsLeakage of amniotic fluid (better prognosis than spontaneous leakage)AmnionitisVaginal bleedingNeedle puncture of the fetusLong term complications:Respiratory distress??Isoimmunization??
12 Amniocentesis and HIV positive women Increased rate of vertical transmissionChemoprophylaxis previous to amniocentesis appears to be beneficial in preventing vertical transmission
13 Multiple Gestation Three methods: Indigo carmine injection to the first sacA 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 higherDetailed description of fetus position and placental location
14 Early Amniocentesis: 9-14 weeks Introduced at late 80th10-14 weeks gestationOnly the amniotic (inner) sac should be aspiratedApproximately 1 cc for gestational ageHigher rate of pregnancy loss, talipes equinovarus, and post procedural amniotic fluid leakagelaboratory failure op to 20%
15 Chorionic villus sampling Was developed in the 80thpercutaneous transabdominal with 19-20g needle
16 Chorionic villus sampling Was developed in the 80thpercutaneous transabdominaltransvaginaltranscervical
19 15-30mg each aspiration20mg ideal for cytogenetic testing30-40mg for cytogenetic and other direct molecular and biochemical tests
20 CVS resultsDirect analysis examines the trophoblast cells of the placenta (very rapidly dividing cells)Results in few hoursgreater vulnerability to mitotic errorCultured analysis examines the fibroblast like cells of the villus stroma or mesenchymal core.Approximately 7-10 daysAccurately reflect the chromosomes of the fetus.
21 Risk of invasive procedure Early amniocentesis:High pregnancy lossHigh fetal malformationsHigh 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 amniocentesisTrans abdominal and transcervical CVS are equally safe and efficacious, provided that centers have expertise with both approachesIn approximately 3–5% of cases, clinical circumstances will support one approach over the otherLimb reduction – not after 9 weeks
23 mosaicismTrue 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 CVS0.1% of pregnancies undergoing amniocentesisClinical 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 fetusTrisomy cells in the placenta and uniparental disomy in the fetus
27 Mosaicism (trisomic cells) in amniotic fluid Probably there are trisomic cells in the fetusThe true level and distribution of trisomic cells cannot be accurately assessed with any prenatal procedureUltrasound is often the best judge of how a baby is developing
28 Uniparental DisomyArises when an individual inherits two copies of a chromosome pair from one parent and no copy from the other parentMaternal UPD – two copies from the motherPaternal 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 isodisomyUnmasking 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 involvedA mosaic finding 18 or 21 is likely to have worse implicationsmosaic 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 tissuesThe tissue affected cannot be evaluatedThe 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 affectedAmniotic fluid suggests that at least one fetal tissue may be affectedFetal 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