invasive procedures for prenatal diagnosis
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Invasive Procedures For Prenatal Diagnosis. Dr. Rahimi Sharbaf Tehran University of Medical Science Women ( Mirza kochak Chan ) Hospital. PRINCIPLES. Diagnosis of fetal chromosomal defects requires invasive testing. - PowerPoint PPT PresentationTRANSCRIPT
Invasive Procedures For Prenatal Diagnosis
Dr. Rahimi SharbafDr. Rahimi Sharbaf
Tehran University of Medical Science Tehran University of Medical Science
Women (Women (Mirza kochak ChanMirza kochak Chan) Hospital) Hospital
PRINCIPLESDiagnosis of fetal chromosomal defects requires invasive testing.Type of procedure depend on many factors: indication, GA, how soon result
Chorionic Villus Sampling (C V S)AMNIOCENTESISFetal Blood Sampling (CORDOCENTESIS)Fetal Tissue Biopsy
BASICS ARE THE SAME
• Positive prenatal screening test( most common) [NON INVASIVE TEST]
• Increased NT• Previous child with chromosome abnormalities• Parent with chromosome abnormality• Fetal anomaly suspected/diagnosed on
ultrasound or IUGR• DNA diagnosis: single-gen disorder, x-linked
disorder • Metabolic disorders• Family history of chromosome abnormality
Indications for Invasive Prenatal Diagnosis
Current evidence suggests thatnon-invasive prenatal testing
Cell-free DNA analysis in maternal plasmaHas the potential to significantly reduce the
number of invasive procedures– Is not diagnostic for the time being
Down syndrome detection rate 98.6% (209/212), false-positive rate 0.20% (3/1371)
Not recommend for low risk & multiple pregnancy
The median and 95th centile of NT at a CRL of
45 mm are 1.2, and 2.1 mm and the respective values at CRL of 84 mm are 1.9 and 2.7 mm
The 99th centile does not change significantly with CRL and it is about 3.5 mm.
Relation between Nuchal Translucency thickness
and prevalence of chromosomal defects
<95th centile 0.2% 95th–99th centiles 3.7% 3.5–4.4 mm 21.1% 4.5–5.4 mm 33.3% 5.5–6.4 mm 50.5% ≥6.5 mm 64.5%
In 2007 ACOG guidelineNot specific age for invasive testing
Elect invasive testing directly
Multiple PregnancyIn multiple pregnancies prenatal diagnosis of chromosomal abnormalities is complicated because:
Firstly: the techniques of invasive testing may provide uncertain results or may be associated with higher risks of miscarriage
Secondly: the fetuses may be discordant for an abnormality, in which case one of the options for the subsequent management of the pregnancy is selective fetocide
Multiple PregnancyShould perform only in a fetal medicine
unite
First trimester chorionicity should be determine
In monochorionic a single amniocentesis may reasonable unless discordance in fetal abnormality or growth
• In pregnancies discordant for chromosomal defects the main options are either selective fetocide or expectant management.
• Selective fetocide after 16 weeks of gestation is associated with three-fold increase in risk of spontaneous abortion compared to reduction before 16 weeks.
Multiple Pregnancy
Amniocentesis OR cvs in twins Amniocentesis is effective in providing a reliable
karyotype for both fetuses and the procedure-related fetal loss rate is about 2%.
In the case of chorionic villus sampling, the procedure-related fetal loss rate is about 1%, but in about 1% of
cases there may be a diagnostic error, either due to sampling the same placenta twice or cross contamination.
The main advantage of chorionic villus sampling is that it provides results sufficiently early to allow for safer selective fetocide.
Invasive Procedures in Hepatitis B & C & HIVUse noninvasive method
Every effort to avoid transvercing placenta
IN HIV if mother is not on antiretroviral therapy and if a fetal needle-stick occurs risk of vertical transmission increase
Post Procedure ConsiderationShould be shown Fetus and fetal heart
activity
Resume normal activity
Defer sexual activity for 24-48
Report=> persistent uterine activity, vaginal bleeding, leakage AF or fever
Injection RhIG in at risk Rh neg ( 300µg)
ComplicationFetal loss rate:
Combination of procedure-related loss +background loss
Most procedure-related loss occur within 2 weeks
procedure-related loss => gestational age, operative experience, type of procedure
Chorionic Villus Sampling
Chorionic Villus Sampling Is the only available method for
prenatal diagnosis in the first trimester
CVS, or placental biopsy perform from 11 weeks & therafter
CVS usually perform transabdominally
Some use transcervical technique ( 2% ) over last few years CVS use increase=>
in some country more than 50% diagnosis of chromosomal abnormality
Invasive Procedures For Prenatal Diagnosis & Treatment
Mirza Kochak Khan Hospital – 1386-87 1386
1387 CVS 276200مورد
385 مورد254 آمنيوسنتز
38 مورد71 كوردوسنتز
IUT 6645 مورد
Chorionic Villus Sampling
A 18-20 gauge spinal needl
Advantage:
Diagnosis in first trimester & rapid diagnosis
Termination in pregnancy easier and saferPregnancy less obvious, more privateMay be less bondingOne major different with Amniocentesis
is AFP for NTD
• Fetal loss no greater than amniocentesis in experience hand
• Ambiguous results/maternal cell contamination ~1-2%
• Culture failure 1-2%• Placental mosaicism ~ 1%
CVS - Complications
• Experience of operator• Number of attempts• Manipulation required• Route of CVS(TA-CVS
preferable)
Who Report 1991
Factors Affecting Rate ofFetal Loss Following CVS
the consensus of the modern literature is that in experienced hands there is little to no ifferences between the procedure risks of amniocentesis and chorionic villus sampling.
However, is clearly that CVS harder to learn and has a steeper learning curve
AMNIOCENTESIS
AMNIOCENTESISFirst perform in 1950
Contain amniocytes, & fetal cell from skin, GU system, gut & biochemical pruducts
Most widely used prenatal diagnostic invasive procedure
Every genetic condition diagnosis able through fetal tissue has been made in amniotic fluid
IndicationChoromosal analysis
DNA diagnosis: single-gen disorder, x-linked disorder
Biochemistry: a-fetoprotein, acetylcholinsterse
Fetal infection
Choroamninitis
Lung maturation
1. Large National Experience2. Lab Techniques Standardized3. Readily Available4. Very Safe5. Very Accurate6. Time to ready answer
Advantages of Mid-Trimester Amniocentesis
AMNIOCENTESISGestational age ( 16-20w) –{Early
amniocentasis}
Comprehensive ultrasound evaluation
Placenta position
Amniotic fluid location
Number of fetus
AMNIOCENTESIS A 20-22 gauge spinal needle
Avoid fetus cord & placenta( if possible)
Continues visualization of the needle avoid: Bloody AF Dry taps Need for multiple insertion 15-20 ml AF (first 1-2 ml discarded)
Bloody Amniotic Fluid(maternal origin) dose not adversely affect culture
Brown AF & dark red & wine colored AF=> increased poor pregnancy outcome
• Fetal Loss 1/400 or less• Minimal fluid leakage <1.0%• Culture Failure 0.5%• Pseudomosaism <0.5%
Problems AMNIOCENTESIS
These values represent the 50th percentile. There is considerable variability around the mean. The 5th, 50th, and 95th percentiles at 33 weeks of gestation are approximately 300, 800, and 1900 mL, respectively. Data from: Brace, RA, Wolf, EJ, Am J Obstet Gynecol 1989; 161:382.
Mean amniotic fluid volume during normal pregnancy
12 weeks 14 weeks 16 weeks
40 ml 100 ml 185 ml
PercutaneousUmbilical Cord Blood
Sampling (PUBS)
Fetal Blood Sampling (FBS)
First was report three decades ago
Was first performed under fetoscopic guidance
Use for diagnosis & treatment
Fetal Blood Sampling
Rapid karyotype
Abnormal ultrasound in second & third trimester
Clarify chromosome mosaicism in amniocetesis or CVS
Assess fetal Hb
• Perform from 18w
• 20-22 gauge needle
• Sample site
• Cardiocentesis
Fetal Blood Sampling
Fetal Blood Sampling complication Hemorrhage
Fetal bradycardia ( most common), fetal monitor at least for 30 minate
Intrauterin infection
Fetal loss ~1% ( 0.2%)
Thank you for attention