Transcript Slide 1
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.
Type of procedure depend on many factors:
indication, GA, how soon result
Chorionic Villus Sampling (C V S)
AMNIOCENTESIS
Fetal Blood Sampling (CORDOCENTESIS)
Fetal Tissue Biopsy
BASICS ARE THE SAME
Indications for Invasive Prenatal
Diagnosis
•
•
•
•
•
•
•
•
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
Current evidence suggests that
non-invasive prenatal testing
Cell-free DNA analysis in maternal plasma
Has 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
95th–99th centiles
3.5–4.4 mm
4.5–5.4 mm
5.5–6.4 mm
≥6.5 mm
0.2%
3.7%
21.1%
33.3%
50.5%
64.5%
In 2007 ACOG guideline
Not specific age for invasive testing
Elect invasive testing directly
Multiple Pregnancy
In 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 Pregnancy
Should 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
Multiple Pregnancy
• 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.
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 & HIV
Use 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 Consideration
Should 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)
Complication
Fetal 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
1387
1386
200
مورد276
CVS
385
مورد254
آمنيوسنتز
38
مورد71
كوردوسنتز
45
مورد66
IUT
Chorionic Villus Sampling
A 18-20 gauge spinal needl
Advantage:
Diagnosis in first trimester & rapid diagnosis
Termination in pregnancy easier and safer
Pregnancy less obvious, more private
May be less bonding
One major different with Amniocentesis is
AFP for NTD
CVS - Complications
• Fetal loss no greater than
amniocentesis in experience hand
• Ambiguous results/maternal cell
contamination ~1-2%
• Culture failure 1-2%
• Placental mosaicism ~ 1%
Factors Affecting Rate of
Fetal Loss Following CVS
•
•
•
•
Experience of operator
Number of attempts
Manipulation required
Route of CVS(TA-CVS
preferable)
Who Report 1991
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
AMNIOCENTESIS
First 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
Indication
Choromosal analysis
DNA diagnosis: single-gen disorder, x-linked disorder
Biochemistry: a-fetoprotein, acetylcholinsterse
Fetal infection
Choroamninitis
Lung maturation
Advantages of Mid-Trimester
Amniocentesis
1.
2.
3.
4.
5.
6.
Large National Experience
Lab Techniques Standardized
Readily Available
Very Safe
Very Accurate
Time to ready answer
AMNIOCENTESIS
Gestational 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
AMNIOCENTESIS
Problems
•
•
•
•
Fetal Loss
1/400 or less
Minimal fluid leakage <1.0%
Culture Failure
0.5%
Pseudomosaism
<0.5%
Mean amniotic fluid volume during normal
pregnancy
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.
40 ml
12 weeks
100 ml
185 ml
14 weeks
16 weeks
Percutaneous
Umbilical 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
Fetal Blood Sampling
• Perform from 18w
• 20-22 gauge needle
• Sample site
• Cardiocentesis
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