Advantages: Non-Invasive: only 5 mL maternal peripheral blood is needed. Therefore, there is no risk of intrauterine infection and miscarriage. Highly Accurate: 100% sensitivity and 99.9% specificity. Early-Test: can be performed at the early pregnancy (~12 weeks), which allows early detection for a better clinical decision. Report: available within 2 weeks. Inclusivity: All chromosomal aneuploidies could be detected in one test. Applications: Those that wish to have non-invasive fetal aneuploidies test for trisomy21, 18 and 13. Those whose age is 35 or above and does not choose to receive invasive prenatal tests. Those whose serum biochemical tests and ultrasound examinations suggest high risk of chromosome aneuploidies at the first and second trimester. Those that has contraindication of invasive prenatal testing, such as placenta previa, risks of miscarriage, HBV infection and HIV infection, etc. Those that received IVF, or previously suffered from habitual abortion.

2. What is Prenatal diagnosis ?
It is the method used to detect
diseases/conditions in a fetus or embryo before
birth.

3.  Maternal age > 35 years at EDC
 Abnormal maternal serum screening for:
1. DS cut off > 1/270
2. Increased risk Trisomy 18 or 13
3. Other genetic abnormalities
 Previous child with chromosomal abnormality or diagnosable
genetic disorder
 Balanced translocation carrier
 Ultrasound anomaly (soft sign vs frank anomaly)

4. Baseline Risk for Having a Child With a
Serious Birth Defect
3-5%

6. Maternal DS Risk All Chrom Abn DS risk
Age Birth Birth Midtrimester
20 1/1231
30 1/185 1/384 1/685
33 1/592 1/285 1/452
34 1/465 1/243 1/352
35 1/385 1/178 1/274
36 1/287 1/149 1/213
37 1/225 1/123 1/166
38 1/177 1/105 1/129
39 1/139 1/80 1/100
40 1/109 1/63 1/80
41 1/85 1/48 1/61

9. Non-
disjunction Normal
Sex cell
production
Monosomy

10. ~70% T21 due to an error in maternal meiosis I
~ 20% maternal meiosis II
~ 5% occur during spermatogenesis (meiosis II)
5% of trisomic 21 error in mitosis- no advanced maternal age and
there is no preference for which chromosome 21 is duplicated in
the mitotic error
most common chromosomal abnormalities in live born children

11. ~1/700

12. Moderate mental retardation
 Facial Characteristics
upslanting palpebral fissures
epicanthic folds,
midface hypoplasia,
macroglossia
Congenital malformations
heart (30-40%), atrioventricular canal
gastrointestinal tract, such as duodenal stenosis or atresia,
imperforate anus, and Hirschsprung disease
Leukemia (both ALL and AML) 10-20x
acute megakaryocytic leukemia occurs 200 to 400 times more
frequently in the Down syndrome
90% have significant hearing loss, usually of the conductive
type

13. Trisomy 18, Edward syndrome
1/8000

14. Facial Central Nervous System
•microcephaly with prominent occiput severe mental retardation
•narrow bifrontal diameter hypotonia -> hypertonia
•short palpabral fissures neural tube defects
•low-set malformed ears poor suck and weak cry
•cleft lip +/- palate failure to thrive
•narrow palatal arch ocular anomalies
•micrognathia Respiratory
Skeletal •apnea
•neck Cardiovascular( >95%)
•webbed •major: VSD, ASD, PDA
•chest •minor: transposition, ToF, coarctation, anomalous
•short sternum coronary artery, dextrocardia,
•widely spaced nipples •aberrant subclavian artery, arteriosclerosis, PS,
•hips: bicuspid aortic and/or pulmonic valves
•small pelvis, congenital dislocation of the hips, limited hip Gastrointestinal
abduction •inguinal, umbilical, and/or
•extremities: diaphragmatic hernia
•phocomelia •congenital defects:
•rockerbottom feet or equinovarus •diastasis recti, heterotopic pancreas, malrotation,
short dorsiflexed big toes Meckel's, tracheoesophageal fistula
fixed flexion deformity of the fingers (overlapping of the Genitourinary
2nd and 5th fingers over the 3rd and 4th fingers) •cryptorchidism
simple arch pattern of the fingers and toes •congenital defects:
hypoplasia of fingernails double ureter, ectopic kidney,
single crease of 5th finger or all fingers (absence of horseshoe kidney, hydronephrosis,
interphalangeal flexion creases) polycystic kidney
simian crease

15. •severe mental retardation
•coloboma,
•(a cleft palate) and/or a cleft lip
•hypotonia
•skeletal abnormalities (polydactyly)
•Renal
heart defects
•holoprocencephaly
1/5,000

16. Second most common major congenital defect (1-2/1000)
Not a chromosome anomaly
Routinely tested and screened for in pregnancy
Failure neural tube to close at 28 days gestation
20% are closed lesions and difficult to detect prenatally

18. Marker Down Syndrome Edward Patau Syndrome
(T21) Syndrome (T18) (T13)
AFP Lower- 25% Lower- 35-55% Slightly raised
uE3 Lower- 30% Lower- 35-55% Lower- 30%
Free HCGβ Raised - 2X Lower- 50% Lower- 50%
PAPP-A Lower- 50% Lower- 50% Lower -50%
Inhibin-A Raised – 2X No value Raised - 2X

20. Test When What Performance* Diagnostic test
T21 30-40% 1.CVS or amniocentesis
Maternal Age > 35 y.o. Age alone T18 30-40% 2. higher miscarriage
rate with T18
NTD no relation
Ultrasound 10-12 Age + NT T21 75-80% CVS or
amniocentesis
T21 60% Amniocentesis
Ultrasound 18-20 Age + T18 85%
sonogram NTD 70-98%
E3 T21 60-70% Amniocentesis
Triple Screen 16-20 (15- msAFP T18 60%
21) BHCG NTD 75-80%
E3 T21 75-80% Amniocentesis
Quad Screen 16-20 (15- msAFP T18 60%
BHCG
21) NTD 75-80%
Inhibin-A
FTS: First PAPP-A T21 83-90% 1.CVS or amniocentesis
Trimester 11-12 (10- Free BHCG T18 80% 2.Need msAFP
Screen, 3. detection of
14) NT NTD -----
miscarriages
Ultrascreen
Integrated 10-14 PAPP-A T21 92% Amniocentesis
Screen 16-20 (15- NT T18 90%
Quad Screen
21) NTD 80%
First trimester serum, stepwise sequential screen, contingency sequential screen *SPR 5%

21. Fetal Anomaly Detection Rate
NTD- AFP alone 75-80%
Trisomy 21- Triple test 70%- Down syndrome
Trisomy 18- Triple test 80%- Edward’s syndrome
*SP = screen positive rate 5%

22.  AMNIOCENTESIS
 CHORIONIC VILLUS SAMPLING
 PERCUTANEOUS UMBILICAL CORD SAMPLING

23. PERFORMED ROUTINELY 16-20 WEEKS

24. Chromosome analysis
AF-AFP levels
ONTD
Acetylcholinesterase
Risk of miscarriage associated with procedure 1/100-1/400
Advantage Disadvantage
Late in gestation
Highly reliable results 99+%
Familiar
oDecision making
Long standing reputation
oPrivacy
oMom feels movement
NTD detection
Fear of needles
Needle invades the sac

25. Performed
>10 wks-13 weeks
Chromosome analysis
Risk 1/100-1/200

26. Disadvantage
Higher loss rate
Less access to procedure
Higher chance of insufficient sample
Early test=risk of sampling a fetus potentially
destined to miscarry
No ONTD testing
More risk of vaginal bleeding/infection.

28. Disadvantage
~2% risk of loss
Technically difficult prior to 20 weeks
Advantages
Blood disorders such as hemophilia and anemia
Useful for detection of Rh isoimmunization of the fetus (blood cell
count and oxygen level)→erythroblastosis fetalis (HDN)
 Fetal karyotype is available in 48 hours to study Chromosomal
abnormalities
Infections such as toxoplasmosis and rubella.
The procedure is also used to perform blood transfusions to the
fetus and to administer medication directly into the fetal blood
supply.

29. RISK Procedure
Fetal Aneuploidy Related
RISK

30. Non-invasive prenatal screening will be based on blood
collection from pregnant women and investigation of the
fetal DNA present in maternal circulation
Advantage
 Do not put the fetus at risk for spontaneous abortion
 Can be offered to all pregnancies
 Provide a more effective prevention
 Done at early pregnancy
 High accuracy

32. What is already Known
Non-invasive prenatal detection of fetal trisomy 21 is achievable by
Next Generation Sequencing (NGS) of maternal plasma DNA
What are the Benefits of NGS
 Among high risk pregnancies clinically indicated for invasive prenatal
diagnosis, noninvasive Detection of fetal trisomy 21 can be achieved
with the use of multiplexed massively Parallel sequencing of maternal
plasma DNA with 100%sensitivity and 99.9% specificity,
 Giving a 99% positive predictive value and 100% negative predictive
value
 The sequencing test could be used to rule out trisomy 21 among high
risk pregnancies before proceeding to invasive diagnostic testing .This
will reduce the number of cases requiring Amniocentesis or chorionic
villus sampling

33.  Multiplexed maternal plasma sequencing / Next Generation
Sequencing has overcome the difficulty that poses the small
proportion of fetal DNA in maternal circulation
 Large-scale validity study used multiplexed maternal plasma DNA
sequencing analysis in pregnant women at high risk for fetal
trisomy 21 to compare the conventional screening who underwent
invasive procedures for full karyotyping
 Research suggested that the invasive diagnostic procedures could
be avoided in about 98% of the cases in a high-risk population
 It is cost-effective and NOW easily obtained from diagnostic
laboratories

34.  Those whose age is 35 or above and do not choose to receive invasive prenatal
tests
 Those whose serum biochemical tests and ultrasound examinations suggest
high risk of chromosome aneuploidies at the first and second trimester
 Those that wish to have non-invasive fetal aneuploidies test for trisomy21, 18
and 13
 Those that received IVF, or previously suffered from habitual abortion
 Those that have contraindication of invasive prenatal testing, such as placenta
previa, risk of miscarriage or infections (HIV, HBV etc)

35. Thank you