invasive procedures for prenatal diagnosis ISUOG Guidelines
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
ī§ 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
ī§ New era dominated by cell-free fetal DNA (cffDNA)
testing: number of invasive procedures for fetal
testing is decreasing dramatically
ī§ Guideline summarizes current information regarding
ī§ when
ī§ how and
ī§ why practitioners perform invasive procedures for
prenatal diagnosis.
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4. 1. AMNIOCENTESIS
ī§ TA aspiration of amniotic fluid from the uterine cavity.
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5. Technique
ī§ A 20â22-G needle should be inserted TA under
continuous US guidance
ī§ Firm entry {prevent tenting of amniotic membrane}
ī§ Avoid
ī§ placental cord insertion site
ī§ placenta is preferable
(especially in Rh-negative women)
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7. ī§ Once the needle has reached the amniotic cavity, the
inner stylet is removed and 15â30mL fluid
(depending on the indication) is aspirated.
ī§ Fluid aspiration may be performed by
ī§ operator
ī§ assistant or
ī§ vacuum device
ī§ The first 2mL of fluid should be discarded
{minimize contamination with maternal cells}
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10. Complications
1. Fetal loss
ī§ 0.1% to 1%
ī§ Risk factors:
ī§ Multiple attempts (3 or more punctures)
ī§ If more than 2 punctures are necessary: delay
the procedure by 24 h
ī§ blood-stained amniotic fluid: may
ī§ reflect current intra-amniotic bleeding
ī§ presence of fetal abnormalities
ī§ Decrease:
ī§ Experience
ī§ an operatorâs competence should be
reviewed when loss rates exceed 4/100
consecutive amniocenteses
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11. 2. Membrane rupture
ī§ 1â2%
ī§ spontaneous sealing is commonly observed
3. Fetal injury and serious maternal complications
rare
ī§ Chorioamnionitis
<0.1%
ī§ Maternal complications
sepsis or even death
Very rare
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12. ī§ Risk factors for fetal loss not been proven
consistently.
ī§ Uterine fibroids
ī§ Mullerian malformations
ī§ Chorioamniotic separation
ī§ Retrochorionic hematoma
ī§ Previous or current maternal bleeding
ī§ BMI >40 kg/m2
ī§ Multiparity (>3 births)
ī§ Vaginal infection
ī§ History of three or more miscarriages
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14. Technique
ī§ The needle should be inserted into the placenta
under continuous US guidance.
ī§ either by the free-hand technique or
ī§ using a biopsy adaptor.
ī§ Access to the placenta may be
ī§ transabdominal or
ī§ transcervical.
ī§ with singleton pregnancy
(gestational age range, 7â12 w):
ī§ fetal loss (2.3% vs 2.5%) and
ī§ successful sampling (95% vs 94%) rates were
similar
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17. Transabdominal approach.
ī§ Local anesthesia may be applied
ī§ Needle:
ī§ single needle of 17â20G or
ī§ two-needle set of outer 17/19G and
ī§ inner 19/20G may be used
ī§ Once the needle has reached the target within the
placenta:
ī§ between one and 10 back-and-forth movements
are performed, while
ī§ vacuum is maintained
ī§ samples are aspirated either
ī§ manually by an assistant or
ī§ with a vacuum adaptor
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18. Transcervical approach.
ī§ Biopsy forceps
ī§ are inserted transvaginally through the cervical
canal to the trophoblastic area, or
ī§ Catheter
ī§ with plastic or metal stylet under syringe
aspiration may be used:
ī§ biopsy forceps Vs. catheter techniques
ī§ comparable placental trauma and effectiveness
ī§ Biopsy forceps: preferred by operators and
patients
ī§ 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.
ī§ Sampling failure: 2.5â4.8% 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
ī§ 0.2% and 2%
ī§ decrease with increasing experience, ranging
between 1/150 and 1/500
ī§ 1.9% (vs 1.4% after amniocentesis)
ī§ in 2016, MA:
ī§ No impact of CVS on fetal loss rates
ī§ risk of miscarriage, 0.21% at 21 days after CVS
ī§ Rate of fetal loss after CVS does not increased
significantly in comparison with the non-
exposed population
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22. ī§ TC vs. TA
ī§ very similar miscarriage rates (2.5% vs. 2.3%)
ī§ TA CVS Vs. 2nd T amniocentesis:
ī§ no significant difference in the total pregnancy loss
ī§ TC CVS vs. 2nT amniocentesis:
ī§ significantly higher risk of
ī§ total pregnancy loss (RR, 1.40 (95% CI, 1.09â1.81)) and
ī§ spontaneous miscarriage (RR, 1.50 (95% CI, 1.07â2.11)
(MA of 4 RCT)
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23. 2. Vaginal bleeding
ī§ 10%
ī§ more frequent after TC (up to 30% of cases) than
after TA approach
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24. 3. Uncommon complications
ī§ amniotic fluid leak
exceedingly rare, <0.5%
ī§ chorioamnionitis and uterine infection
extremely small
ī§ pre-eclampsia and IUGR
ī§ some reports
ī§ {placental damage}
ī§ MA: failed to show an association
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25. ī§ Risk factors for complications
Lower fetal loss rates if
ī§ âĨ100 procedures are performed per annum
ī§ operatorâs competence should be reviewed
when
ī§ loss rates âĨ 8/100 and
ī§ sampling failure âĨ 5/100 consecutive CVS
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26. ī§ Increased risk for miscarriage
ī§ African-American maternal race
ī§ At least 2 aspirations/ needle insertions
ī§ Heavy bleeding
ī§ Maternal age younger than 25 y
ī§ Gestational age at CVS <10 w
ī§ Fetal structural anomalies and increased nuchal
translucency thickness (NT)
ī§ Lower levels of PAPP-A in maternal serum have
{association of low PAPP-A levels with placental disorders}
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27. ī§ Increase the risk of fetal loss not proven consistently.
ī§ Advanced maternal age
ī§ Uterine malformations
ī§ Chorioamniotic separation
ī§ Retrochorionic hematoma
ī§ Previous or current maternal bleeding
ī§ Retroverted uterus;
ī§ Post-procedure persistent fetal bradycardia
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29. ī§ Approaches to the umbilical vein for FBS:
ī§ Cordocentesis at
ī§ placental cord insertion site or
ī§ free loop and
ī§ Puncture of the intrahepatic portion of the vein via
the fetal liver.
ī§ Cordocentesisâ
ī§ US-guided puncture of the umbilical cord (umbilical
vein), for either
ī§ Diagnostic (FBS) or
ī§ Therapeutic
ī§ intrauterine transfusion or
ī§ drug instillation
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32. Timing
ī§ beyond 18+0 completed weeks of gestation
{ risk of fetal loss is increased before this stage}
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33. Technique
ī§ A 20â22-G needle is introduced transabdominally
under continuous US guidance and inserted into the
umbilical vein.
ī§ The free-hand technique is used more commonly,
although the use of a needle guide is preferred by
some.
ī§ If the placenta is anterior
ī§ a puncture of the cord at the level of placental
insertion is suggested;
ī§ If the placenta is posterior
ī§ a free loop of the cord or
ī§ intra-abdominal portion of the umbilical vein is
sampled
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35. ī§ Once the needle appears to have reached the target,
flushing with saline may be used to confirm its correct
position.
ī§ Care should be taken to avoid the umbilical arteries.
ī§ Aspiration by syringe is attempted by
ī§ an assistant or
ī§ the operator until blood is obtained in the sample.
ī§ Origin of the blood should be confirmed by
ī§ microscope (automated blood analyzer) to assess
the mean corpuscular cell volume, or
ī§ using a rapid acidification test (i.e. Kleihauer Betke
or Apt test)
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37. ī§ The intrahepatic vein an alternative site
ī§ when
ī§ cord access is difficult or
ī§ sampling fails at the placental cord insertion site
ī§ Additional advantages
ī§ absence of cord complications
ī§ reduced risk of fetal blood loss and fetomaternal
hemorrhage
ī§ certainty of the fetal origin of the sample.
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38. Complications
ī§ Risk of complications or sampling failure
decrease with increasing experience of the operator.
1. Fetal loss
ī§ between 1% and 2%
ī§ Factors associated with increased risk
ī§ fetal anomalies
ī§ IUGR
ī§ gestational age <24 w.
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39. 4. ELIGIBILITY FOR INVASIVE PRENATAL
DIAGNOSIS
âĸ Counseling
ī§ should precede any invasive procedure
ī§ benefits,
ī§ risks
ī§ technical aspects.
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40. ī§ Indications
increased risk for
1. fetal chromosomal abnormality
2. hereditary genetic or metabolic disease
3. some perinatal infections.
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41. īą COUNSELING
ī§ carried out by
ī§ specialist in obstetrics or in fetal medicine who
performs the procedure or
ī§ geneticist or
ī§ dedicated midwife
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42. ī§ Information:
ī§ benefits and risks of invasive prenatal diagnosis vs
screening
ī§ differences between CVS and amniocentesis
ī§ accuracy of results,
ī§ complications
ī§ different timing
ī§ type of termination of pregnancy in case of
abnormal results
ī§ need for anti-D passive immunization post-
procedure if the woman is Rhesus negative and
non-immunized
ī§ Consent:
ī§ written
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43. Indications for amniocentesis or CVS
ī§ increased risk of
I. fetal aneuploidy
II. genetic or biochemical disease of the fetus,
III. maternal transmittable infectious disease
ī§ under certain circumstances, maternal request.
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44. I. Increased risk of fetal aneuploidy may derive from a
1. screening test
ī§ first-trimester combined test
ī§ cffDNA test/non-invasive prenatal test (NIPT)
2. second-trimester biochemistry
ī§ triple or quadruple test
3. abnormal ultrasound findings
ī§ fetal structural anomaly commonly associated
with chromosomal abnormality
4. obstetric history
ī§ Previous fetus or child affected by aneuploidy
5. family history
ī§ parental carrier of chromosomal balanced
translocation or inversion
ī§ parental aneuploidy or mosaicism for aneuploidABOUBAKR ELNASHAR
45. ī§ Not an indication:
ī§ Advanced maternal age (>35 years)
ī§ although in some countries it is still among the
accepted criteria for invasive testing
ī§ Conception by ART
ī§ 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:
ī§ Family hereditary disease with a known mutation
or biochemical change
ī§ Male fetus and carrier status of pregnant woman
for a disease with X-chromosomal inheritance
ī§ Carrier status of both parents for an autosomal
recessive disorder.
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47. III. Maternal transmittable infectious disease
ī§ maternal primary infection or seroconversion
involving
ī§ toxoplasma
ī§ cytomegalovirus or
ī§ rubella,
ī§ To
ī§ confirm or
ī§ exclude transmission of the infection to the
fetus.
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48. īą Maternal request
ī§ not a valid indication
ī§ though under exceptional circumstances
ī§ acute parental anxiety, and after extensive
counseling
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49. Indications for FBS
ī§ The commonest indications
1. chromosomal mosaicism after amniocentesis
2. hematological assessment of the fetus
ī§ quantification of fetal anemia or
ī§ platelet/lymphocyte count
ī§ Extremely rare indications
ī§ having been replaced largely by CVS and
amniocentesis
ī§ full karyotype
ī§ blood type or platelet antigen status
ī§ genetic testing
ī§ Infection
ī§ 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
ī§ Prophylactic anti-D immunoglobulin to
ī§ non-sensitized women
ī§ 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
ī§ full karyotype,
ī§ rapid testing:
ī§ QF-PCR (or, more rarely, FISH), may be carried
out on villi or amniotic fluid to test for specific
chromosomes
ī§ These tests provide results in 1â2 days
ī§ molecular diagnosis of chromosomal imbalances
ī§ Microarray techniques
ī§ diagnosis of monogenic disease.
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