2. PRENATAL DIAGNOSISIts the science of identifying structural or
functional abnormalities-birth defects-in the fetus.
FETAL THERAPYIt is used to improve the intrauterine environment
for fetal benefit.
it includes•
Blood product transfusion.
•
•
•
•
•
Transplacental medication.
Laser or radiofrequency ablation of vascular anastomoses.
Amnioreduction.
Shunt placement.
Extensive fetal surgery.
3. Why Prenatal screening/diagnosis ?
• All the pregnant women are at risk of carrying a fetus with genetic
abnormalities.
•Incidence of major abnormality apparent at birth is 2 to 3%.
(callens 5th edi)
•Principal goal of prenatal diagnosis is to supply information to at risk
families so they can make informed choice during pregnancy.
•Potential benefits of prenatal diagnosis are
1) early reassurance to at risk families if results are normal.
2) Risk information to couples who would not have child without
defects.
3) Allowing couples to prepare for the birth of an affected child.
4) Risk information to couples for whom termination is an
option.
(From callens 5th edi)
4. • Background risk depends on maternal age and
gestational age at time of evaluation. ( Risk increases
with age and decreases with gestational age), so
prenatal screening should be an integral part of ANC
care, not to be limited to high risk population (ACOG
2007).
5. Genetic counseling
• Clinical Genetics is the discipline concerned with the
diagnosis and management of the medical, social, and
psychological aspect of hereditary diseases.
• Genetic counseling is an integral part of genetic testing
/prenatal Testing.
• The process of genetic counseling involves components
like
1)validation of diagnosis
2)obtaining the family history,
3)estimation of risk of recurrence
4)and by all these helping the family to reach
decisions and take appropriate action and follow up.
• Nondirective counseling is adopted as standard, In this
patients are not told what decision to make with regards to
testing and management options but, instead, are provided
information and support.
6.
7.
8.
9. First Trimester Screening
Screening methods1.
2.
3.
4.
5.
6.
7.
Age of mother.
Nuchal translucency.
Nasal Bone.
Free Bhcg + PAPPA-P.
NT + Free Bhcg + PAPPA-P(combined test).
Secondary
Ductus venosus sonography.
screening
Tricuspid Regurgitation Doppler study.
tools
10. Age
• Risk of Downs syndrome and any aneuploidy increases with
age.
• Women with age 35 years and singleton pregnancy and age of
31 years with twins (dizygotic), put women into high risk group
of fetal aneuploidy.
11. Table Showing risk of chromosomal abnormalities in
Liveborn infants.(from callens 5th edi.)
Maternal Age
Risk of Downs syndrome
Total risk for chromosomal abnormalities
20years
1/1667
1/526
25years
1/1250
1/476
30 years
1/1000
1/384
34 years
1/500
1/238
35 years
1/385
1/192
40 years
1/100
1/66
43years
1/50
1/33
45 years
1/30
1/21
49 years
1/11
1/8
12. Nuchal Translucency
• Nuchal
Translucency(NT) refers to the normal subcutaneous
fluid filled space between the back of the neck and underlying
skin.
• Single most powerful marker available today for differentiating
Downs syndrome from euploid pregnancy in 1st trimester.
• NT is not specific for aneuploidy its also increased in
1. CHD
2. Genetic syndrome
3. Abnormal or delayed development of lymphatic.
• Time – 10 to 14 weeks ( CRL of 36 to 84mm). (from callens 5th edi.)
13.
14.
15. • Requirements for accurate NT measurement.
1. CRL length between 36-84mm.
2. Good midsagittal section showing facial profile.
3.Clear clarification between the fetal skin and amnion
achieved by spontaneous or induced fetal movements.
4.Magnification of image so that fetal head, neck, upper
thorax, occupy three-fourth of screen.
5.Fetal head should be in neutral position. Extended head
will increase and flexed head will decrease the measurement.
6.Reading should be taken in line of the fetal mandible
that usually corresponds to area of widest NT.
Nuchal translucency quality control is maintained by national
body like in UK its Fetal Medicine foundation who periodically audit
interact with sonologist and accredit them for doing NT.
( Callens 5th edi)
16. NT usefulness
• NT is single most sensitive marker of aneuploidy chances
of abnormality in fetus increases in direct proportion to
increase in NT value.
Sr
No.
NT Values
% of abnormal fetuses
1.
2.5 to 3.4 mm
8%
2.
3.5 to 4.4 mm
29%
3.
4.5 to 5.4 mm
48%
4.
>6.5 mm
87%
(F Arias 3rd edi)
17. •The overall Down’s syndrome detection rate is 64% to 70% at 5%
false positive rate. (from Williams 23rd).
• There are three major trial conducted for detection rateSr
no.
Trial
Geographical
area
Population
studied
Detection rate of
Downs syndroem
1.
SURUSS trial (sr urine
and usg study)
UK
General
population
63%
2.
BUN trial
(Biochemistry, USG,
NT)
US
High risk
group
69%
3.
FASTER trial (First
and Second trimester
eveluation of risk)
Multicentric
prospective
trial
General
population
64 to 70%.
(ACOG 2007)
18. NT usefulness
• The measurement of NT is above 95th percentile in 71.8% of
fetuses with Downs syndrome, and in 70.5% of fetuses with other
chromosomal defects ( T 18, T 13, Turners, triploidy)
71.8% of fetuses
with Downs
syndrome, 70.5%
of fetuses with
other
chromosomal
defects
5th percentile
95th percentile
(From F Arias 3rd edi.)
19. • when used in combination with free Beta-Hcg and PAPP-A----Detection rate of
Downs syndrome is 79% to 87%.
First trimester screening
And detection rate ( from Williams 23rd)
Strategy
Analytes
Detection rate at 5%
false positive rate
USG for NT
Nuchal Translucency
64 to 70%
Combined 1st
trimester
screening
NT, free beta-hcg, PAPP-A
79 to 87%
• If NT is ≥ 3.5 mm significant risk of aneuploidy ----appropriate to perform
invasive testing..
• NT is also useful marker of cardiac anomalies, diaphragmatic hernia, skeletal
dysplasia, genetic syndrome.
( Williams 23rd edi)
20. NT in multiple gestation.
1. NT is single most useful tool in screening multiple
gestation.
2. Maternal serum screening results are misleading
1)Serum markers are approx but not exactly, twice
those found in singleton pregnancy so relative
contribution from each fetus cant be determined.
2) Single maternal serum value is used to provide
information about multiple fetus and there are no clear
cut guidelines to individualize the risk.
3) In discordant cases, normal fetus will mask the
abnormal marker produced by affected twin.
2. NT measurement in first trimester can evaluate each fetus
individually and give risk assessment.
21. Combined 1st trimester screening
• Pregnancies with Downs syndrome are associated with altered
levels of serum free beta hcg and PAPP-A.
Beta HCG
1. In Downs syndrome both free alpha and beta subunits are
increased, but free beta subunit( Unique) is used for screening.
2. In Downs syndrome placenta is hypersecretory and immature
leading to increased secretion of Beta HCG by
syncytiotrophoblast.
3. This increase starts at end of the 1st trimester and continues
during 2nd trimester. (used in both trimester).
4. Free beta hCG Levels are higher, MOM concentration is ≥2.0
in affected pregnancies. (from williams 23rd)
5. When used alone detection rate is 33% (from F arias)
22. PAPP-A
1. Its concentrations are lower in pregnancies with aneuploidy,
but difference with normal pregnancies becomes smaller with
advance in gestational age.
2. Ideal time 10 to 14 weeks.
3. Levels are reduced, MOM concentration is 0.38 in affected
cases.
4. When used alone detection rate is 38%. ( F arias 3rd edi)
these 1st trimester serum markers are largely independent
of NT, so combining serum and sonographic screening protocol
is more effective strategy then alone.
FOR a 5% false positive rate, the Downs syndrome detection
rates using combined 1st trimester test is 79 to 87%.
23. Nasal Bone (NB)
• Absent nasal bone on USG done at 11 to 13 weeks is another
marker of Downs syndrome.
• Absence of Nasal bone is not related to NT and can be
combined in one scan.
• Detection rate of Downs syndrome using absent nasal bone is
67%.
• When combined with NT detection rate is 90%. (F Arias)
• Nasal bone detection requires expertise and strictly following
criteria for how to take measurement.
• No clear recommendation of its use.
• Role as second line screening tool in high risk patients and
not as a general population screening tool.
24. Requirement of accurate NB measurement
1) Midsagittal plane.
2) Fetal spine should be
posterior.
3) slight flexion at neck
4) Head and thorax occupy
whole image.
5) Face of transducer should
be parallel to the
longitudinal axis of the
nasal bone and skin over
bridge.
6) Two parallel lines
representing the skin over
the nasal bridge and nasal
bone compose of ―equal
sign‖.
7) If bottom part of = sign is
missing, nasal bone is
considered absent.
1st Line showing Skin
( Callens 5th edi)
2nd line –Nasal bone
25. .
First trimester Ductus venosus sonography
• 1st Trimester Ductus venosus blood flow is an adjunctive test
For fetal aneuploidy screening.
• Forward triphasic pulsatile flow is normal.
•Reversed flow at time of atrial contraction is abnormal.
26. Ductus venosus sonography usefulness
•Associated with fetal aneuploidy and fetal cardiac
malformation.
• 59% to 93% of aneuploid fetus has abnormal ductus venosus
flow.( Callens 5th edi)
•Ductus venous Doppler is difficult as ductus venosus vessel at
10 to 14 week measures 2mm. So difficult to locate and difficult
to obtain accurate flow velocity wave form without
contamination of waveforms of neighboring vessel like IVC
showing reversal of flow during contractions normally.
•As secondary screening tool, to be performed by experienced
sonologist.
• for modifying the final risk for aneuploidy or to help predict
prognosis of fetuses with normal chromosome and increased
NT.
27. First trimester Tricuspid Regurgitation(TR)
• Abnormal tricuspid regurgitation in 1st trimester is associated
with fetal aneupoidy.
• TR is considered to be present if a regurgitant jet of at least
60cm/sec is noted extending to over half of systole
• Down syndrome detection rate during 11 to 13 weeks is 68%
alone.
•Its Easy to obtain TR waveform in comparison to Ductus
venosus waveform.
• Not recommended for routine screening, has a role as second
line screening test (following an initial high risk NT and serum
screen) with detection rate of 92%.
(from Callens 5th edi)
30. Triple Test
• Most commonly used serological test in 2nd trimester.
• It consist of measuring
1) MSAFP (maternal serum alpha fetoprotein).
2) Beta Hcg.
3) uE3 (unconjugated estriol).
• These three variables are independent predictors of genetic
risk and in combination with maternal age generate a patient
specific risk of having downs syndrome.
• Time – 15 to 20 weeks. ( As before 15 weeks there is close
overlap of serum markers value in affected and non affected
pregnancies.)
• Detection rate 60 to 69%.
(from Callens 5th edi)
31. Triple test
• Triple test screens for following fetal disorders.
Disorders MSAFP
uE3
Beta hCG Inhibin A
Open NTD
increased
No change
No change
No change
Downs
syndrome
decreased
decreased
increased
Increased
Trisomy 18
decreased
decreased
No change
No change
Table showing the pattern of results seen in triple and Quad test
screening . (from callens 5th).
32. ALPHA FETO PROTEIN•
•
•
•
•
Glycoprotein synthesized by fetal yolk sac in early pregnancy and
later by fetal GIT and liver.
Major serum protein analogous to albumin.
Concentration increases in both fetal serum and amniotic fluid
until 13 week, after which levels rapidly decreases, conversely its
concentration in maternal serum increases after 12 week.
Normal ration is 1,00000 : 1 (fetal to maternal serum) When the
fetal serum level is 2 million u/l the corresponding amniotic fluid
AFP is 20,000 u/L, and maternal serum level is 20u/l
Fetal body wall defects uncovered by integument such as NTD,
ventral wall defect, permits AFP leak in amniotic fluid and leads to
its increased concentration in maternal serum, Further in Downs as
fetal liver is immature its production is less and rapid removal
from fetal circulation so, its concentration in maternal serum.
( Callens 5th edi)
33.
34. Conditions associated with abnormal level of MSAFP
ELEVATED LEVELS
• Underestimation of gestation age.
• Multifetal gestation.
• IUD
• NTD
• Gastroschisis and omphalocele
• Low maternal weight
• Pilonidal sinus
• Esophageal or intestinal obstruction.
• sacrococcygeal teratoma.
• Urinary obstruction
• Renal anomalies- Polycystic kidneys,
renalagenesis, congenital nephrosis. ( as
high as > 10 MOM)
•Congenital skin defects
•Cloacal extrophy
•Chorioangioma of placenta
• Placental abruption
• Oligohydroamnios
•Preeclampsia
•Low birth weight
•Maternal Hepatoma or teratoma
35. Conditions associated with abnormal level of MSAFP
LOW LEVELS
• Obesity
• Diabetes
• Chromosomal Trisomy.
• GTD
•Fetal death
• overestimated gestational age.
36. MSAFP usefulness
• MSAFP as a component of triple test should be routinely
advised in pregnancy.
• Results are expressed in MOM and MSAFP level of 2.0 to 2.5
MOM used as upper limit of normal.
• 90% detection rate for anencephaly and 80% for spinabifida at
MOM 2 to 2.5 as upper limit. (from Williams 23rd).
• Several factors influence the MSAFP and taken into
consideration when calculating AFP MoM
Maternal weight
Gestational Age
Diabetes
Multifetal gestation.
38. Follow up When MSAFP is elevated.
• Amniocentesis and determination of AFAFP (Amniotic fluid
AFP) and AChE (acetylcholinestarase).
• AFAFP and AChE in combination has a 97% detection rate
for NTD.
• AChE is more specific to neural tissue then AFAFP.
• Detection of AChE in amniotic fluid generally indicate an
open NTD.
Although increased AChE levels are also seen in
1) Omphalocele.
2) Gastroschisis.
3) cystic hygroma.
4) fetal hydrops.
39.
40. Unconjugated Estriol
• uE3 is synthesized in placenta, its concentration is
decreased in Downs syndrome independent of AFP and hCG
levels.
• In downs syndrome primary abnormality involves lack of
cholesterol precursor probably due to immature liver function
rendering placenta unable to produce uE3.
• Women with low uE3 (<0.75MOM) are also at risk of—
1) IUGR.
2) Oligohydroamnios
3) Delivery of small for gestational age infants.
4) Those with very low <0.15 MOM at risk of Metabolic and
genetic disorder (like Steroid sulphatase def, kallman
syndrome,CAH)
41. Triple test
• For Downs syndrome and Trisomy 18
1.
2.
For downs syndrome, the values of serum markers is converted
into patient specific risk, 1:250 is taken as cut off
and detection rate is 60% to 69%. (from F arias)
For Trisomy 18, the serum concentration of all three analytes is
low and 1:100 is taken as cut off and detection rate is 80%.
Multiple marker screening tests are based on a composite
likelihood ratio determined by levels of all analytes. The maternal
age related risk is then multiplied by this ratio and we obtain
patients risk. A positive test indicates increased risk, but its not
diagnostic of Trisomy or other aneuploidy. Conversely, a negative
screening test indicates that risk is not increased but doesn’t
duarantee normal fetus.
42. Quadruple (Quad) test
• The quad test consist of determining the maternal serum
concentrates of
1) MSAFP
2) Beta Hcg
3) Free estriol
4) Inhibin A
• Time – 15 to 20 weeks
• The addition of Inh A to triple test markers will improves the
detection rate of downs syndrome in comparison to triple.
• It has detection rate up to 81%
• Level of Inh A in range of 1.8 MoM .
43. Combined 1st and 2nd trimester
screening
1) Integrated screening –
• combines both 1st and 2nd trimester screening test into
single risk.
• Highest downs syndrome detection rate- 90% to 96%.
• Disadvantage being test results are not available until
the second trimester test has been complete.
44. 2) Sequential screeningThis test obviate some of the disadvantages seen
in integrated test in this test, result of 1st trimester
screening are disclosed to women at highest risk, thus
allowing them the option of earlier invasive testing and
those at lowest risk can still take advantage of higher
detection rate achieved with second trimesterscreening.
• There are two testing strategies
1) Stepwise sequential screening2) Contingent sequential screening-
45. • Stepwise sequential screening• In this strategy women determined to be at high risk ( Downs
syndrome risk above predetermined cutoff) after 1st trimester
screening are offered genetic counseling and option of diagnostic
testing, those at low risk offered 2nd trimester screening and both
1st and 2nd trimester results are used for final risk thus increasing
detection rate in low risk women and allows early confirmation in
high risk women.
• Detection rate is 95%.
Contingent sequential screening• This strategy classifies women as having High Low and
Intermediate risk based on 1st trimester screening.
•High risk– CVS Low risk—No further screenig
Intermediate risk—2nd trimester screening.
• Number of patient entering in 2nd phase are less.
• Detection rate is 88 to 94%.
47. INVSIVE PRENATAL DIAGNOSIS TECHNIQUES
• Pre procedure genetic counselingPre procedure counseling is necessary as it will allow
patients to understand their situation allow them to give
consent(or withhold) for the procedure.
Following points to be explained-1. The chance that fetus will be affected.
2. Nature and consequences of disorder.
3. Risks and limitation of procedure.
4. Time required for reporting.
5. Possibility of complications of the procedure such as
procedure related fetal loss, failed attempt to obtain a testable
sample.
50. Midtrimester amniocentesis
1.
2.
Midtrimester amniocentesis is performed at 15 to 20 weeks of
gestation.
Prerequisite for midtrimester amniocentesis
1. Pre procedure Genetic counseling.
2. Comprehensive USG determining
A) number of fetuses.
B)Gestational age.
C)Placental localization. (for identifying place of puncture).
D) Also rule out congenital anomalies.
3. ABO RH status of the patient.
51. •STEPS OF AMNIOCENTESIS1. Under all aseptic precautions a
20 or 22-G needle is used, under
USG guidance needle is inserted
in two rapid steps.
2. Once in amniotic cavity fluid is
aspirated 1st ml of fluid is
discarded because of possible
contamination.
3. Total of 20ml of fluid is aspirated
and used for fetal karyotyping and
for AFP levels.
4. At end of procedure puncture site
is observed with help of USG for
any bleeding and fetal cardiac
activity is documented at end of
procedure.
5. Bloody tap is discarded as it
overestimate the AFP levels.
52. Amniocentesis with multiple sacs.
• Requires separate puncture and analysis of amniotic
fluid of each sac.
• Indigo carmine dye (0.5 to 1.0cc) mixed with 5cc of
AF and injected into 1st sac, allows better identification
of 2nd sac. Methylene blue dye is not used as associated
with hemolysis in fetus.
• Dye injection to be given only in cased where 2nd sac is
not identify easily.
• Care should be taken not to puncture intervening
membrane.
53. Indications of Amniocentesis
• Diagnostic
1. Detection of chromosomal abnormalities.
a. Downs syndrome
b. Trisomy 18, 13.
c. Inborn errors of metabolism.
d. Sex linked disorder – Turners, klinefelters, fragile x
syndrome.
e. NTD – by AFAFP levels
2. Fetal lung maturity by measuring ratio of Lecithin and
sphingomycelin in later pregnancy.
3. Spectrometric analysis of AF determination of degree of fetal
hemolysis in Rh neg mother.
• Therapeutic
1. Decompression of polyhydroamnios.
(From F Aris )
54. 1. Complications
1. Transient vaginal discharge or amniotic fluid leakage in 1
to 2%
2. Chorioamnionitis in <0.1%.
3. Procedure related loss
According to the FASTER trial the
procedure related loss rate was 1/300 to 1/700
i.e. 0.6-0.14% but the results were questioned on ground
of methodology but further studies showed loss rate of
1/200 to 1/300 (ACOG 2007).
1. Fetal injury 1 in 1000.
2. Miscarriage rate – 0.5%
( Williams 23rd)
55. Early Amniocentesis
• Procedure is performed between 11 to 14 weeks.
• Disadvantages as compare to midtrimester amniocentesis
1) Procedure at this gest age is more challenging due to lake of
membrane fusion to uterine wall.
2) Higher rate of complications like
1) Club foot (1.3%).
2) Amniotic fluid leakage.
3) Fetal loss (7.6%) According to CEMAT trail( Canadian Early
and mid trimester Amniocentesis trial allocated women to
early and mid trimester groups and shown procedure related
loss 7.6% in early group and discouraged the early
amniocentesis.
4) More cell culture failure requiring second procedure.
•Recommendations are against the use of early amniocentesis.(ACOG 2007)
56. ACOG Recommendations(2007) on
INVASIVE TESTING
• LEVEL A
1) Early Amniocentesis should not be performed because of higher
risk of pregnancy loss and complications compared with traditional
amniocentesis.
• LEVEL B
1) Amniocentesis at 15 weeks of gestation or later is a safe procedure,
procedure related loss is less than 1 in 300 to 500.
2) In experienced individual and centers, CVS procedure-related loss
rate may be the same as those for amniocentesis.
LEVEL C
1) Invasive testing should be available to all women, regardless of
maternal age.
2) Patients with increased risk of fetal aneuploidy includes
Women with a previous fetus or child with an autosomal Trisomy or sex
chromosome abnormality, one major or at least two minor fetal structural
defects identified by USG, either parent with chromosomal translocation,
inversion, or parental aneuploidy.
3) Non directive counseling before prenatal diagnostic testing does
not require a patient to commit to pregnancy termination if the results is
abnormal.
57. Chorionic Villus Sampling (CVS)
• CVS, a biopsy of the developing placenta is performed at 10 to
13 weeks of gestation for indications similar to Amniocentesis.
• Advantages over Amniocentesis are
1.
Performed earlier in gestation.
2.
Early diagnosis and patient can have option of 1st
trimester abortion. (more safer then 2nd trimester.)
• Two commonly used approaches
1) Transcervical
2) Transabdominal.
• Sample consist of placental tissue (~20 mg).
58. 20 G needle is
used in
Transabdominal
CVS
16 G polyethylene
catheter with a
flexible, stainless
obturater is used in
Transcervical CVS
59. Transcervical Vs Transabdominal
Transcervical
•
•
•
•
•
•
•
Placenta in lower 1/3rd
Technically simple to perform.
More comfortable to patient.
Relative contraindications– Positive N gonorrhea culture
– Active genital herpes.
– Active bleeding.
– Extreme uterine Ante or
Retroflexion.
Fetal loss rate slightly higher then
amniocentesis.
Rupture of membrane ~0.3%
Light Vaginal bleeding ~8%.
Transabdominal
• Placenta in upper 2/3rd.
• Difficult specially if
placenta is posterior.
• Discomfort is greater.
• Fetal loss rate identical to
Amniocentesis ~ 0.7%
Incidence of Limb reduction defects higher if CVS is performed around 7
weeks, if performed by an experienced operator after 10 weeks incidence of
limb reduction same as background risk.(WILLIAMS OBSTRICS)
60. Cytogenetic analysis
Amniocentesis
Amniocyte culture over a period of 10 to 14 days.
Amniocytes are arrested during
metaphase stage of cell division
Total
time
Amniocyte harvestation, fixed on slide
and stained with dye.
Around
21 days
Chromosomes are then examined under microscope.
Final Karyotyping report
61. Figure showing G Banded male karyotype
•Giemsa staining-producing specific
banding pattern
called G banding is
most widely used
technique.
• Each chromosome
stains in a
characteristic pattern
of light and dark
bands.
• so involvement of
any particular band
in any chromosomal
abnormality can be
detected precisely.
62. Rapid test for Karyotype Analysis
• FISH (Florescence In Situ Hybridization)
Allows visualization of small region on chromosome too small
to be identified by karyotyping.
Results available with in 24 to 72 hrs. ( as compare to
karyotyping around 21 days.) as done on interphase state.
Fluorescent DNA probes are used with same nucleotide
sequence as the stretch of chromosomal DNA of interest.
Probe will hybridize at 2 places reflecting homologous nature
normally.
If probe hybridizes at > 2 places detects trisomy.
64. Quantitative Fluorescent PCR
• Another rapid technique.
• Uncultured aminocytes from 1 to 2 ml of amniotic fluid are
collected and DNA is extracted.
• Chromosome specific short tandem repeats of DNA from
selected chromosome are then amplified using markers.
• Using an automated scanner, the intensity of fluorescence
present for each short tandem repeat is quantified and the number
of chromosome alleles derived.
• QFPCR identifies aneuploidy and is used in some centers as an
alternative to FISH.
65. Fetal Blood sampling
( Cordocentesis)
•It is performed for assessment
and treatment of confirmed Red
cell or Platelet alloimmunization
and in evaluation of nonimmune
hydrops.
• Detecting sever fetal anemia.
•Fetal Blood also can be
obtained for genetic analysis
when CVS or
AMNIOCENTESIS results are
confusing.
•Blood can also be analyzed for
metabolic disorders
hematological
disorders
Acid base analysis.
immunological studies.
66. Fetal blood sampling
• Under USG guidance 22 G spinal needle is used to
puncture umbilical vein.
• Arterial puncture should be avoided may result in
vasospasm and bradycardia.
• Complications include
•Cord vessel bleeding- 50%
•Cord hematoma-17%
• Fetal- maternal hemorrhage- 66% with ant placenta and 17%
with posterior placenta.
•Fetal bradycardia-3to 12%.
•Fetal death-1.7%
(Williams 23rd)
67. Fetal tissue biopsy
• There are many genetic conditions for which there is
no specific molecular test is available.
•Prenatal diagnosis can only be done by biopsy of fetal
part under USG guidance.
• eg. 1)Muscle biopsy to diagnose muscular dystrophy or
mitochondrial myopathy.
2)Skin biopsy for diagnosis of epidermolysis
bullosa.
68. Pre Implantation Genetic diagnosis
• With use of ART (assisted reproductive technologies), Zygotes
affected with a severe genetic disorder can be identified so that
they are not used for IVF, as a result only unaffected embryos are
selected for implantation.
• Can diagnose nearly 200 different single gene disorders.
•Two different techniques are used
1)Polar body analysis (already in metaphase suitable for FISH)
2)Blastomere biopsy at 6 to 10 cell stage (3 day old)- one
totipotent cell is removed)
• Recommendations are against use of this technology solely for
advanced maternal age, that it does not improve IVF fertilization
success, and it may be detrimental.
(Williams 23rd)
69. Fetal cells in maternal circulation
• Fetal cells are present in all pregnant women, although
the concentration is very low only 2 to 6 cells per ml.
•Isolation of these cells and use in prenatal diagnosis
will obviate need for invasive procedure.
• Most important thing is fetal cells sorting techniques
which uses fetal cell surface markers for sorting fetal
cells, but no universal fetal cell marker is yet identified
hampering clinical implication of this technology.
•Further its not possible to have fetal cells witout
maternal cell contamination and isolation of sufficient
quantity of cells for use is also difficult.
74. Introduction to Genetic sonogram
•It’s a specific targeted examination for fetal aneuploidy,
most specific for Downs syndrome, that searches for the
presence of
1)Fetal structural anomalies
2)Aneuploidy markers and
3)Abnormal biometry.
(Callen’s 5th)
• These aneuploidy markers are called as ―soft‖ markers
and these are variations in normal anatomy that, except for
their relationship to aneuploidy, are unlikely to be
clinically significant.
(Callen’s 5th)
• soft markers are often transient and nonspecific findings
which can also occur frequently in euploid fetuses.
75. Genetic Sonogram
•Sensitivity of genetic sonogram ranges from 84%
among women with advanced maternal age to 90%
among women younger than 35 years with abnormal
triple test.
• Performed between 18 to 20 weeks of gestation.
• Major advantage is, it reduces the invasive testing rate
and can optimize the selection of candidate for invasive
testing in order to minimize the procedure related losses
of normal fetuses without significantly decreasing
detection rate.
(Callen’s 5th)
76. Candidate for Genetic sonogram
Low risk vs. high risk population
• Inappropriate for LOW RISK population
1)High false positive rate of 12 to 15% in high risk
population (which is probably more in low risk).
2)Each marker by itself has only low to moderate
sensitivity for Downs, when found in isolation it not necessarily
increase the risk but increases cost and anxiety in LOW RISK.
3) In LOW RISK patient the prior risk may be so low that
Presence of one marker will not qualify a patient for
Amniocentesis.
4) Further the accuracy of soft markers has only been
studied in HIGH RISK population and generalizing the result in
low risk is not appropriate.
80. Most investigated ―Six Soft markers‖ of downs syndrome with
likelihood ratio
( Williams 23rd edi)
81. Second Trimester Ultrasound Markers Practice
Guidelines
Normal Ultrasound (No marker present)
Low Risk
Including
1)Age < 35 and
2)serum screen negative
No testing required
From (Callen’s 5th)
High Risk
Including Age
1) Age≥ 35years
or 2) Serum screen positive
or Both
Downs syndrome risk
adjustment (80% reduction in a
priori risk)
82. Second Trimester Ultrasound Markers Practice
Guidelines
ONE ISOLATED SOFT MARKER PRESENT ( Except Nuchal
Fold or Absent nasal bone)
Low Risk
Including
1)Age < 35 and
2)serum screen negative
No testing required
From (Callen’s 5th)
High Risk
Including Age
1) Age≥ 35years
or 2) Serum screen positive
or Both
Offer Genetic Amniocentesis
83. Second Trimester Ultrasound Markers Practice
Guidelines
≥ 2 SOFT MARKERS PRESENT OR Thick Nuchal fold OR
Absent nasal bone OR structural anomaly
Low Risk
Including
1)Age < 35 and
2)serum screen negative
Offer Genetic Amniocentesis
From (Callen’s 5th)
High Risk
Including Age
1) Age≥ 35years
or 2) Serum screen positive
or Both
Offer Genetic Amniocentesis
