1. Supachai Nathongchai, MD.
Prenatal screening
&
Diagnosis
Prenatal screening
&
Diagnosis
Supachai Nathongchai, MD.
Department of Obstetrics and Gynecology
SomdejprachoaTaksinmaharaj Hospital

2. Population (pregnant women)
Concept of Screening
Population (pregnant women)
Screening test
Screen Positive
Screen Negative
Diagnostic test
Amniocentesis
CVS
Fetal blood sampling
No further test

3. Prenatal Screening
Structural abnormalities
Chromosome abnormalities

4. Chromosome abnormalities
Trisomy 21
Trisomy 13
Trisomy 18
Monosomy X
Triploidy

5. Chromosome abnormalities
Prenatal diagnosis
Chorionic villous sampling
Amniocentesis
Fetal blood sampling
Preimplantation genetic diagnosis
But !
All methods subject to risk of miscarriage

6. Screening for Down syndrome
Maternal age
Ultrasonography
Maternal blood tests
Combined

7. Incidence of Down syndrome
35 years
1/386
1/274
Maternal age LB
2nd trim.
25 years
1/1250
1/887
30 years
1/965
1/685
35 years
1/386
1/274
38 years
1/182
1/129
40 years
1/100
1/78
45 years
1/31
1/22

8. Maternal age for DS screening
Age > = 35 yr.
10 %
20-30 %
Age > 35 yr.
90 %
70-80 %
Age group
Pregnancy
DS baby

9. Women < 35 years
low risk
70-80% of Down syndrome
Neglected

10. Ultrasonography First trimester screening Nuchal translucency (NT)
Nasal bone

11. Observations on an ethnic classification of idiots
Langdon Down
“ ….. The nose is small. The skin has a slight dirty yellowish tinge, and is different in elasticity, giving the appearance of being too large for the body.”

12. Nuchal Translucency (NT)

13. Nuchal translucency (NT)
Measurement of NT

14. Nuchal translucency (NT)
Measurement of NT

15. Measurement of nuchal translucency
The maximum thickness of the subcutaneous translucency between the skin and the soft tissue overlying the cervical spine should be measured by placing the callipers on the lines as shown. During the scan, more than one measurement must be taken and the maximum one should be recorded. + + + + + + + + + +

16. Measurement of (NT) CRL 45-84 mm GA 11-13 wk Fetus Sagittal section
Neutral position
Occupies 3/4 of image

17. Reference range of fetal nuchal translucency with CRL showing the 5th, 25th, 50th, 75th and 95th centiles
The week scan. The diagnosis of fetal abnormalities

18. Likelihood ratios for trisomy 21 in relation to the deviation in fetal nuchal translucency thickness
The week scan. The diagnosis of fetal abnormalities

19. Recent studies examining the implementation of fetal nuchal translucency screening at 10-14 weeks
Authors N
Risk cutoff
DR(%)
FPR(%)
Snijders et al
96,127
1 in 300
82.2
8.3
Theodoropoulos et al
3,550
91.0
4.9
Adekunle et al
11,398
76.0
4.7
Schwarzler et al
4,523
83.0
Gasiorek-Wiens et al
23,805
87.6
13.0
Zoppi et al
12,495
90.0
9.0
Brizot et al
2,996
7.4
DR = Detection rate ; FPR = False positive rate

20. Observations on an ethnic classification of idiots
Langdon Down
“ ….. The nose is small. The skin has a slight dirty yellowish tinge, and is different in elasticity, giving the appearance of being too large for the body.”

21. Absence of nasal bone in fetuses with trisomy 21 at 11-14 weeks of gestation
Cicero S, et al. The Lancet 2001

22. Estimated sensitivity and false positive rate for risk cutoffs in screening for trisomy 21
Risk NT screening NT and NB screening
cutoff Sensitivity (%) FPR (%) Sensitivity (%) FPR (%)
1 in
1 in
1 in
1 in
1 in
1 in
1 in
1 in
1 in
1 in
Cicero S, et al. The Lancet 2001

23. Nuchal translucency in twin pregnancies
Sebire NJ,e t al. Br J Obstet Gynaecol 1996
448 twin pregnancies
Fetal nuchal translucency thickness was measured by ultrasound examination at weeks
Sensitivity and false positive rates of screening for trisomy 21 were calculated
The sensitivity is similar to that in singleton pregnancies
The specificity is lower because translucency is also increased in chromosomally normal monochorionic twin pregnancies

24. Fetal karyotyping in twins
In twin pregnancies, selection of the appropriate invasive technique depends on the:
Accuracy of obtaining a result from both fetuses
Procedure-related risk of fetal loss
The risks of selective fetocide should the pregnancy be found to be discordant for an abnormality and the parents choose this option

25. Fetal karyotyping in twins
There is an additional advantage of screening by measurement of nuchal translucency thickness; when there is discordancy for a chromosomal abnormality, the presence of a sonographically detectable marker (increased nuchal translucency) helps to ensure the correct identification of the abnormal twin should the parents choose selective termination.

26. 3-D ultrasound measurement of fetal nuchal translucency
It can be used to replicated nuchal translucency measurements only when nuchal skin can also be clearly seen on 2-D ultrasound.
Paul C, et al. Ultrasound Obstet Gynecol 2001
The possibility of rotating a stored volume and inspecting it in three orthogonal planes makes 3-D ultrasound a useful tool for nuchal translucency measurements, especially in doubtful cases.
Clementschitsch G, et al. Ultrasound Obstet Gynecol 2001

27. Conditions associated with increased nuchal translucency
Cardiac defects
Diaphragmatic hernia
Exomphalos
Achondrogenesis type II
Achondroplasia
Asphyxiating thoracic dystrophy
Beckwith-Wiedemann syndrome
Blomstrand
osteochondrodysplasia
Body stalk anomaly
Campomelic dysplasia
EEC syndrome
Fetal akinesia-
deformation sequence
Fryn syndrome
GM1-gangliosidosis
Hydrolethalus syndrome

28. Ultrasound screening of Down syndrome
The second trimester
Ultrasound screening of Down syndrome

29. Genetic Sonogram: Ultrasound indicators for Down
1. Structural anomalies
: Cardiac anomaly, DU atresia
2. Soft marker
: Echogenic intracardiac foci
Pyelectasis, Femur length Humerus Length

30. Structural anomalies
Trisomy 13
Trisomy 18
Trisomy 21
90%
70-80%
20%

31. Soft ultrasound makers
Nuchal skin fold thickness
Choroid plexus cyst (CPC)
Mild ventriculomegaly
Nasal bone
Echogenic intracardiac foci (EIF)
Echogenic bowel
Renal pyelectasia
Hypoplastic middle phalanx of the fifth digit

32. Nuchal skin fold thickness
Langdon Down (1866)
=  thickness of skin of the back
Benacerraf et al (1985)
= Using as an U/S marker for Down

33. Fig NT

34. Cut off threshold of nuchal thickness
> 6 mm.
16-20 wks gestation
Down abnormal nuchal thickness 40%
LR: 17 (CI 8-35) => Expert review is recommended, and karyotyping should be offered
Sensitivity 34%
Specificity 99.5%

35. Nuchal thickness : Efficacy
Associated with
- Congenital heart disease Genetic syndromes (rare)
=> Expert review is recommended

36. Choroid plexus cyst (CPC)
Cyst > 3 mm
14 to 24 weeks’ gestation
Locate in lateral ventricle
Related more to Trisomy 18
Not associated with other fetal abnormalities or abnormal postnatal development.

37. CPC and Trisomy 18
Snijders et al (1994) Trisomy 18 (58 cases) CPC 50% Normal fetusesCPC 1%
Isolated CPCminimal increase risk

38. Isolated CPC Trisomy 18 Trisomy 21 Size, Disappearance and Laterality
LR (trisomy 18) = 7 (CI 4-12)
Trisomy 21
Likelyhood ratio = 1.87 (CI )
Size, Disappearance and Laterality
=> not increase or reduce risk
Gross et al 1995, Gupta et al 1997 , Yoder et al 1999

39. Recommendation
Fetal karyotyping should only be offered if isolated CPCs are found in women 35 years or older or if the maternal serum screen is positive for either trisomy 18 or 21
All women with fetal CPCs and additional malformation should be offered referral and karyotyping
All women with CPCs and additional soft markers should be offered additional counselling and further ultrasound review

40. Mild ventricular dilatation
Lateral ventricle : constant along gestation
mm.
Male : female = 6.4 :5.8 mm
Definition mm.
Dangling choroid plexus > 3 mm.from medial wall

42. Isolate mild ventriculomegaly
 abnormal fetal karyotype ~ 3.8% (0-28.6%)
 0.15% of chromosomally-normal fetuses
 1.4% of trisomy 21 fetuses in the second trimester
 LR 9

43. Recommendations
Neonatal assessment and follow-up are important to rule out associated abnormalities and are important because of the potential for subsequent abnormal neurodevelopment
Cerebral ventricles greater than or equal to 10 mm are associated with chromosomal and central nervous system pathology. Expert review should be initiated to obtain the following:
a detailed anatomic evaluation looking for additional malformations or soft markers
laboratory investigation for the presence of congenital infection or fetal aneuploidy
MRI as a potential additional imaging technique

44. Echogenic intracardiac focus (EIF)
A bright focus in papillary muscle
Attach to cordae tendinae
Move with valvar movement
Calcium deposit and surrounded by fibrous tissue
Bettelheim et al 1999
Lt ventricle 96%
Both ventricle 4.3%
Rt ventricle 4.7%

45. Fig

46. EIF : Rt ventricle : Both ventricle
Bromley 1998
EIF : Rt ventricle
: Both ventricle
Twice the risk
Wax + Philput 1998
EIF : Multiple
: Dense echo
Increase risk

47. Location of EIF The evidence is best for left or biventricular EICF
LR 2.8 (95% CI ) =>high-risk women.
Low-risk => LR 0–1.8
Consensus of the SOGC Imaging and Genetics Committees suggests an LR of 2

48. Recommendations
EICF should be evaluated as part of the 4-chamber cardiac review during the 16- to 20- week ultrasound
Isolated EICF with a fetal aneuploidy risk less than 1/600 by maternal age (31 years) or maternal serum screen requires no further investigations
Women with an isolated EICF and a fetal aneuploidy risk greater than 1/600 by maternal age (31 years) or maternal serum screening should be offered counselling regarding fetal karyotyping
Women with right-sided, biventricular, multiple, particularly conspicuous, or nonisolated EICF should be offered referral for expert review and possible karyotyping

49. Echogenic bowel echogenicity of abdominal content
Compare to liver and bone echo
Associated with
- Trisomy 21
- Congenital infection
- Meconeum ileus (cystic fibrosis)
- Bowel atresia
- FGR, FDIU

50. Echogenic bowel Nyberg et al : Grading system
Grade 1 : mild echogenic ; diffuse
Grade 2 : mod echogenic ; focal
Grade 3 : Very echogenic ; bone echo

51. Echogenic bowel Echogenic bowel seem to increase risk
% of all 2nd trimester fetuses
Increased risk for fetal aneuploidy =>LR 6 (CI )
Sensitivity 14.7%
Specificity 98%
Echogenic bowel seem to increase risk
The more the echo, The higher the risk
Deren et al 1998

52. Recommendations
1. Evaluation of the fetal bowel should be done routinely during week obstetric ultrasound.
2. Echogenic bowel should be identified by comparison with the echogenicity of surrounding bone using an appropriate transducer and gain setting. Bowel echogenicity equal to or greater than bone is significant (grade 2 or 3).
3. No further investigation are required for grade 1 echogenic bowel

53. 4. Grade 2 and 3 echogenic bowel is associated with both chromosomal and nonchromosomal abnormalities. Expert review is recommended to initiate the following:
a. detailed ultrasound evaluation looking for additional structural anomalies or other soft markers of aneuploidy
b. detailed evaluation of the fetal abdomen looking for signs of bowel obstruction or perforation
c. detailed evaluation of placental characteristics (echogenicity, thickness, position, and placental cord insertion site)
d. genetic counselling
e. laboratory investigations that should be offered, including fetal karyotype, maternal serum screening, DNA testing for cystic fibrosis (if appropriate), and testing for congenital infection

54. MILD PYELECTASIS
5 mm mm

55. MILD PYELECTASIS Isolated pyelectasis 0.7%
Isolated finding in fetal Down syndrome ~ 2%
LR for Down syndrome ~ 1.9 (95% CI 0.7–5.1)

56. Recommendations
1. Evaluation of fetal kidneys is a part of the screening ultrasound at 16 to 20 weeks,’ and if pyelectasis is visualized, the renal pelvis should be measured in the anterior/posterior diameter
2. All fetuses with renal pelvic measurements > 5 mm should have a neonatal ultrasound, and those having measurements > 10 mm should be considered for a third trimester scan
3. Isolated mild pyelectasis does not require fetal karyotyping
4. Referral for pyelectasis should be considered with additional ultrasound findings and (or) in women at increased risk for fetal aneuploidy owing to maternal age or maternal serum screen results

57. SHORT FEMUR LENGTH Below 2.5th percentile or
Less than 0.9 of that predicted by the measured BPD
Sensitivity 16%
FPR 4%
LR 2.7 (95% CI )

58. SHORT HUMERUS LENGTH Below 2.5th percentile or
Less than 0.9 of that predicted by the measured BPD
Sensitivity 9%
FPR 3%
LR 7.5 (95% CI )

59. FIFTH FINGER CLINODACTYLY
3.4% of normal fetuses
18.8% of fetuses with Down syndrome.
LR 5.6 (95% CI 2.5–11.9).

60. RISK ASSESSMENT

61. The Scoring Index Major anomaly 2 Nuchal fold > 6 mm 2
Short femur 1
Short humerus 1
Pyelectasis > 4 mm 1
Hyperechoic bowels 1
Echogenic intracardiac focus 1
J Ultrasound Med 11: , 1992

62. Modified scoring index Sensitivity 86.8%; False positive rate 27.1%
Maternal age Maternal age >
Scoring index > 2
Sensitivity 86.8%; False positive rate 27.1%

63. Abnormal genetic sonogram one or more abnormal USG markers
sensitivity 87%
specificity 91%
positive predictive values 11%
negative predictive values 99.8%
Yeo L, Vintzileos AM: The use of genetic sonography to reduce the need for amniocentesis in women at high risk for Down syndrome. Semin Perinatol 27: , 2003

64. Likelihood Ratios for Down
Major anomaly 25.0
Nuchal fold 18.6
Hyperechoic bowels 5.5
Short humerus 2.5
Short femur 2.2
Echogenic intracardiac focus 2.0
Pyelectasis 1.6
No markers 0.4
Ultrasound Obstet Gynecol 1998;12:8-14.

65. The Extended Genetic Sonogram

66. Screening Modalities Maternal age Ultrasonography Biochemical markers
Combined screening

67. Maternal age + free bhCG + PAPP-A Detection rate for Down 60%

68. “Combined testing” Nuchal translucency and free bhCG and PAPP-A
Brizot et al 1994/1995
Orlandi et al 1997
de Graaf et al 1999
De Biasio et al 1999
Spencer et al 2000
Studty Trisomy GA FPR(%) DR(%) 80 11 37 13
210
10-14
5.0
3.3 89 87 85

69. Second Trimester Biochemical Screening
Triple Screening
Alpha-fetoprotein
Human chorionic gonadotropin
Unconjugated estriol
Other markers
Dimeric inhibin A
Dried blood, urine markers

70. Objective : To increase prenatal detection of
Down syndrome (DS)
Neural tube defects (NTD)
Trisomy 18
Timing ONLY between weeks

71. AFP hCG uE3
Trisomy 21
Open NTD
Trisomy 18

72. Factors affecting triple analytes levels
Gestational age
Maternal weight
Ethnicity
Multiple pregnancy
Smoking
Type I diabetes mellitus

73. Screen positive for NTD (AFP > 2.5 MoM)
USG
Confirm GA
R/O twins, gross anomalies
Repeat AFP test
Targeted USG
Brain (Lemon and Banana signs)
Spine

74. Screen positive for DS (DS risk) > 1:270
USG
Confirm GA
R/O twins, gross anomalies
Genetic counselling
risk of DS based on age and TS results
risk of amniocentesis (1:200)

75. Screen positive for trisomy 18 (Trisomy 18 risk > 1:100)
USG
Confirm GA
R/O gross anomalies
Genetic counselling
risk based on age and TS results
risk of amniocentesis (1:200)

76. Triple screen Negative
DS screening efficacy - 70% for women under 35 years - 90% for women 35 years and over
Open NTD Screening efficacy - 95% for anencephaly - 80% for spinal bifida

77. Second trimester comparable US screening vs Biochemical screening
Sensitivity
False positive
Biochemical
Reduce risk : more
No need for highly skilled physician
Combine test : most benefit
comparable

78. Diagnostic tests (Gold standard)
Karyotyping
Down syndrome
Trisomy 18
Targeted ultrasonography
Open neural tube defects

79. Prenatal diagnosis
Prenatal diagnosis has been called “one of the most powerful advances in medical technology.”

80. Amniocentesis Technique Blindly
Static ultrasound (late 1970s and early 1980s)
Real-time ultrasound
- Marking
- Ultrasound guidance

81. Amniocentesis Technique 16-20 weeks’ gestation
20-22 guage spinal needle
Approximately 20 ml of amniotic fluid is collected
The first 1-2 ml of amniotic fluid is discarded to minimise the chances of maternal cell contamination

82. Amniocentesis Safety The Canadian Collaboration Trial 1020 pregnancies
No difference in loss rates from that of controls
Correlation between fetal losses and > 2 insertions per procedures and the needles of 19-guage or higher

83. CVS Technique 9-12 weeks’ gestation Transcervical or transabdominal
(Equally safe and efficacious )
The chorion frondosum, which contains the most mitotically active cells, is the area of the placenta that is sampled

84. Fetal blood sampling Technique Cordocentesis or Percutaneous
umbilical blood sampling (PUBS)
2. Intrahepatic vein sampling
3. Cardiocentesis
* 2 & 3 are associated with increased risks

85. PUBS Technique 20-22 guage needle.
The most commonly used location is within 2 cm. of the placental insertion.
Fetal blood have been obtained from umbilical artery, but generally the umbilical vein is preferred because it is larger and less likely to be associated with a fetal bradycardia.

86. Diagnostic embryofetoscopy
History
Embryoscopy was first performed via the transcervical approach early in gestation, previous to fusion of the chorion and amnion, to make a phenotypic diagnosis.
Percutaneous techniques were then developed to introduce the fetoscope directly into the amniotic cavity transabdominally.

87. 7 weeks’ gestation

88. 14 weeks’ gestation

89. 16 weeks’ gestation

90. Recommendation Offer amniocentesis or CVS to Offer screening to
Women age 35 years and over at EDC
Previous aneuploidy
Offer screening to
Women age 34 years or under at EDC
Women age 35 years and over who are reluctant to accept amniocentesis