ABOUBAKR ELNASHAR

1. INVASIVE PROCEDURES
FOR PRENATAL
DIAGNOSIS
The International Society of Ultrasound in
Obstetrics and Gynecology (ISUOG)
2016
Prof. Aboubakr Elnashar
Benha university, Egypt
ABOUBAKR ELNASHAR

2. CONTENTS
 INTRODUCTION
1. AMNOCENTESIS
2. CHORIONIC VILLOUS SAMPLING
3. FETAL BLOOD SAMPLING
4. ELLIGABILITY
5. TYPES OF GENETIC TESTING
6. CHECKLIST BEFORE AND AFTER THE
PROCEDURE
ABOUBAKR ELNASHAR

3. INTRODUCTION
 New era dominated by cell-free fetal DNA (cffDNA)
testing: number of invasive procedures for fetal
testing is decreasing dramatically
 Guideline summarizes current information regarding
 when
 how and
 why practitioners perform invasive procedures for
prenatal diagnosis.
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4. 1. AMNIOCENTESIS
 TA aspiration of amniotic fluid from the uterine cavity.
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5. Technique
 A 20–22-G needle should be inserted TA under
continuous US guidance
 Firm entry {prevent tenting of amniotic membrane}
 Avoid
 placental cord insertion site
 placenta is preferable
(especially in Rh-negative women)
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7.  Once the needle has reached the amniotic cavity, the
inner stylet is removed and 15–30mL fluid
(depending on the indication) is aspirated.
 Fluid aspiration may be performed by
 operator
 assistant or
 vacuum device
 The first 2mL of fluid should be discarded
{minimize contamination with maternal cells}
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9. Timing
at or beyond 15+0 weeks of gestation.
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10. Complications
1. Fetal loss
 0.1% to 1%
 Risk factors:
 Multiple attempts (3 or more punctures)
 If more than 2 punctures are necessary: delay
the procedure by 24 h
 blood-stained amniotic fluid: may
 reflect current intra-amniotic bleeding
 presence of fetal abnormalities
 Decrease:
 Experience
 an operator’s competence should be
reviewed when loss rates exceed 4/100
consecutive amniocenteses
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11. 2. Membrane rupture
 1–2%
 spontaneous sealing is commonly observed
3. Fetal injury and serious maternal complications
rare
 Chorioamnionitis
<0.1%
 Maternal complications
sepsis or even death
Very rare
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12.  Risk factors for fetal loss not been proven
consistently.
 Uterine fibroids
 Mullerian malformations
 Chorioamniotic separation
 Retrochorionic hematoma
 Previous or current maternal bleeding
 BMI >40 kg/m2
 Multiparity (>3 births)
 Vaginal infection
 History of three or more miscarriages
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13. 2. CHORIONIC VILLUS SAMPLING (CVS)
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14. Technique
 The needle should be inserted into the placenta
under continuous US guidance.
 either by the free-hand technique or
 using a biopsy adaptor.
 Access to the placenta may be
 transabdominal or
 transcervical.
 with singleton pregnancy
(gestational age range, 7–12 w):
 fetal loss (2.3% vs 2.5%) and
 successful sampling (95% vs 94%) rates were
similar
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16. Approaches to CVS:
transcervical ( red horizontal arrow ) and
transabdominal ( green vertical arrowABOUBAKR ELNASHAR

17. Transabdominal approach.
 Local anesthesia may be applied
 Needle:
 single needle of 17–20G or
 two-needle set of outer 17/19G and
 inner 19/20G may be used
 Once the needle has reached the target within the
placenta:
 between one and 10 back-and-forth movements
are performed, while
 vacuum is maintained
 samples are aspirated either
 manually by an assistant or
 with a vacuum adaptor
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18. Transcervical approach.
 Biopsy forceps
 are inserted transvaginally through the cervical
canal to the trophoblastic area, or
 Catheter
 with plastic or metal stylet under syringe
aspiration may be used:
 biopsy forceps Vs. catheter techniques
 comparable placental trauma and effectiveness
 Biopsy forceps: preferred by operators and
patients
 The amount of villi obtained in the sample must be
checked visually: minimum amount of 5mg villi in
each sample is required to achieve a valid result.
 Sampling failure: 2.5–4.8% of proceduresABOUBAKR ELNASHAR

19. Timing
should not be performed before 10+0 completed
weeks of gestation
{higher risk of fetal loss and complications before this
time}
The limbs and mandible seem to be more susceptible to
vascular disruption before 10 w
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21. Complications
1. Fetal loss
 0.2% and 2%
 decrease with increasing experience, ranging
between 1/150 and 1/500
 1.9% (vs 1.4% after amniocentesis)
 in 2016, MA:
 No impact of CVS on fetal loss rates
 risk of miscarriage, 0.21% at 21 days after CVS
 Rate of fetal loss after CVS does not increased
significantly in comparison with the non-
exposed population
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22.  TC vs. TA
 very similar miscarriage rates (2.5% vs. 2.3%)
 TA CVS Vs. 2nd T amniocentesis:
 no significant difference in the total pregnancy loss
 TC CVS vs. 2nT amniocentesis:
 significantly higher risk of
 total pregnancy loss (RR, 1.40 (95% CI, 1.09–1.81)) and
 spontaneous miscarriage (RR, 1.50 (95% CI, 1.07–2.11)
(MA of 4 RCT)
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23. 2. Vaginal bleeding
 10%
 more frequent after TC (up to 30% of cases) than
after TA approach
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24. 3. Uncommon complications
 amniotic fluid leak
exceedingly rare, <0.5%
 chorioamnionitis and uterine infection
extremely small
 pre-eclampsia and IUGR
 some reports
 {placental damage}
 MA: failed to show an association
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25.  Risk factors for complications
Lower fetal loss rates if
 ≥100 procedures are performed per annum
 operator’s competence should be reviewed
when
 loss rates ≥ 8/100 and
 sampling failure ≥ 5/100 consecutive CVS
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26.  Increased risk for miscarriage
 African-American maternal race
 At least 2 aspirations/ needle insertions
 Heavy bleeding
 Maternal age younger than 25 y
 Gestational age at CVS <10 w
 Fetal structural anomalies and increased nuchal
translucency thickness (NT)
 Lower levels of PAPP-A in maternal serum have
{association of low PAPP-A levels with placental disorders}
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27.  Increase the risk of fetal loss not proven consistently.
 Advanced maternal age
 Uterine malformations
 Chorioamniotic separation
 Retrochorionic hematoma
 Previous or current maternal bleeding
 Retroverted uterus;
 Post-procedure persistent fetal bradycardia
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28. 3. FETAL BLOOD SAMPLING (FBS)
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29.  Approaches to the umbilical vein for FBS:
 Cordocentesis at
 placental cord insertion site or
 free loop and
 Puncture of the intrahepatic portion of the vein via
the fetal liver.
 Cordocentesis’
 US-guided puncture of the umbilical cord (umbilical
vein), for either
 Diagnostic (FBS) or
 Therapeutic
 intrauterine transfusion or
 drug instillation
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32. Timing
 beyond 18+0 completed weeks of gestation
{ risk of fetal loss is increased before this stage}
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33. Technique
 A 20–22-G needle is introduced transabdominally
under continuous US guidance and inserted into the
umbilical vein.
 The free-hand technique is used more commonly,
although the use of a needle guide is preferred by
some.
 If the placenta is anterior
 a puncture of the cord at the level of placental
insertion is suggested;
 If the placenta is posterior
 a free loop of the cord or
 intra-abdominal portion of the umbilical vein is
sampled
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34. ABOUBAKR ELNASHAR

35.  Once the needle appears to have reached the target,
flushing with saline may be used to confirm its correct
position.
 Care should be taken to avoid the umbilical arteries.
 Aspiration by syringe is attempted by
 an assistant or
 the operator until blood is obtained in the sample.
 Origin of the blood should be confirmed by
 microscope (automated blood analyzer) to assess
the mean corpuscular cell volume, or
 using a rapid acidification test (i.e. Kleihauer Betke
or Apt test)
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36. ABOUBAKR ELNASHAR

37.  The intrahepatic vein an alternative site
 when
 cord access is difficult or
 sampling fails at the placental cord insertion site
 Additional advantages
 absence of cord complications
 reduced risk of fetal blood loss and fetomaternal
hemorrhage
 certainty of the fetal origin of the sample.
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38. Complications
 Risk of complications or sampling failure
decrease with increasing experience of the operator.
1. Fetal loss
 between 1% and 2%
 Factors associated with increased risk
 fetal anomalies
 IUGR
 gestational age <24 w.
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39. 4. ELIGIBILITY FOR INVASIVE PRENATAL
DIAGNOSIS
• Counseling
 should precede any invasive procedure
 benefits,
 risks
 technical aspects.
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40.  Indications
increased risk for
1. fetal chromosomal abnormality
2. hereditary genetic or metabolic disease
3. some perinatal infections.
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41.  COUNSELING
 carried out by
 specialist in obstetrics or in fetal medicine who
performs the procedure or
 geneticist or
 dedicated midwife
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42.  Information:
 benefits and risks of invasive prenatal diagnosis vs
screening
 differences between CVS and amniocentesis
 accuracy of results,
 complications
 different timing
 type of termination of pregnancy in case of
abnormal results
 need for anti-D passive immunization post-
procedure if the woman is Rhesus negative and
non-immunized
 Consent:
 written
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43. Indications for amniocentesis or CVS
 increased risk of
I. fetal aneuploidy
II. genetic or biochemical disease of the fetus,
III. maternal transmittable infectious disease
 under certain circumstances, maternal request.
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44. I. Increased risk of fetal aneuploidy may derive from a
1. screening test
 first-trimester combined test
 cffDNA test/non-invasive prenatal test (NIPT)
2. second-trimester biochemistry
 triple or quadruple test
3. abnormal ultrasound findings
 fetal structural anomaly commonly associated
with chromosomal abnormality
4. obstetric history
 Previous fetus or child affected by aneuploidy
5. family history
 parental carrier of chromosomal balanced
translocation or inversion
 parental aneuploidy or mosaicism for aneuploidABOUBAKR ELNASHAR

45.  Not an indication:
 Advanced maternal age (>35 years)
 although in some countries it is still among the
accepted criteria for invasive testing
 Conception by ART
 However, ICSI because of oligospermia:
parents should be informed that there is an
increased risk of chromosomal anomalies in the
sperm causing infertility which may be
transmitted to male offspring.
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46. II. Increased risk for a known genetic or biochemical
disease of the fetus may derive from:
 Family hereditary disease with a known mutation
or biochemical change
 Male fetus and carrier status of pregnant woman
for a disease with X-chromosomal inheritance
 Carrier status of both parents for an autosomal
recessive disorder.
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47. III. Maternal transmittable infectious disease
 maternal primary infection or seroconversion
involving
 toxoplasma
 cytomegalovirus or
 rubella,
 To
 confirm or
 exclude transmission of the infection to the
fetus.
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48.  Maternal request
 not a valid indication
 though under exceptional circumstances
 acute parental anxiety, and after extensive
counseling
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49. Indications for FBS
 The commonest indications
1. chromosomal mosaicism after amniocentesis
2. hematological assessment of the fetus
 quantification of fetal anemia or
 platelet/lymphocyte count
 Extremely rare indications
 having been replaced largely by CVS and
amniocentesis
 full karyotype
 blood type or platelet antigen status
 genetic testing
 Infection
 plasma or serum studies (e.g. metabolites,
hormones). ABOUBAKR ELNASHAR

50. 5. CHECKLIST BEFORE AND AFTER THE
PROCEDURE
1. The Rhesus status of the mother
2. Presence of alloantibodies
 Prophylactic anti-D immunoglobulin to
 non-sensitized women
 within 72 h post-procedure unless father Rh
negative.
3. Screening for blood-borne viruses
HBV & HCV; HIV is not recommended.
4. The main principles of asepsis
Antibiotic prophylaxis: not recommended.
5. Report
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51. 6. TYPES OF GENETIC TESTING: WHAT TO LOOK
FOR
 full karyotype,
 rapid testing:
 QF-PCR (or, more rarely, FISH), may be carried
out on villi or amniotic fluid to test for specific
chromosomes
 These tests provide results in 1–2 days
 molecular diagnosis of chromosomal imbalances
 Microarray techniques
 diagnosis of monogenic disease.
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52. Thanks
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