1. IN THE NAME OF GOD First trimester screening for aneuploidy
Dr.parichehr pooransari perinatalogist
SHOHADA hospital of shahid beheshti university

2. Why to diagnose prenatally?
Is better to know!
preparing family for dealing with anomaly
planning time and place of delivery
Multideciplinary mx
In-utero treatment
Termination of pregnancy
Prematurity and congenital anomalies
are the most common causes of neonatal
death

3. How to Diagnose? Diagnostic Procedures Therapeutic Procedures
Screening Procedures
Diagnostic Procedures
Therapeutic Procedures

4. Screening procedure
Screening is intended to identify populations who have an increased risk for a specific disorder, and for whom diagnostic testing may be warranted.

5. Screening by Sonography
Confirmation of gestatioanl age
Confirmation of viability
Detection of number of fetus and chorionicity
Detection of fetal anomalies
Detection of high risk groups for chromosomal abnormalities
Detection of placental site
Detection of amniotic fluid volume
Detection of fetal growth
Detection of fetal Well-being
Evaluation of fetus and placental blood flow
Detection of fetal anemia ( Isoimmunization),…

6. Screening by biochemical markers
Screening and diagnosis of maternal anemia
Screening and diagnosis of GDM
Screening of maternal diseases ( Hypothyroidism,…)
Screening of chromosomal abnormalities
Screening and diagnosis of fetal infections
Screening of fetal anemia
Screening of preterm birth
Screening of Intrauternine growth restriction and SGA
Screening for macrosomia
Screening for miscarriage and stillbirth
Screening for preeclampsis
Screenongfor neural tubal defects

7. Screening for Chromosoaml abnormalities
First trimester Versus Second trimester
Sonography
Biochemistry
Combined sonography and biochemistry

8. Assessment of Risk Maternal age
0.0001
0.001
0.01
0.1 1 10 20 25 30 35 40 44
Years
Risk %
Trisomy 21
Trisomy 18
Trisomy 13
xxx/xxy/xyy
45x
Triploidy
For every case of trisomy 21 there is one with another defect
The risk for trisomies increases with maternal age
The risk for sex chromosome defects and triploidy does not change with maternal age

9. Measurement of Nuchal Translucency
Gestation wks
CRL mm
Mid-sagittal view
Image size: calipers 0.1mm
Neutral position
Away from amnion
Maximum lucency
Callipers on-to-on
More than one measurement
Umblical cord around the neck

11. Technique: maximum lucency
Screening for Trisomy 21
Technique: maximum lucency
200
400
600
800
1000
1200
1400 1 2 3 4 5
Nuchal translucency (mm)
Risk (1 in)
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0 45 55 65 75 85
Crown-rump length (mm)
NT (mm)
2.7mm
2.0mm
1.5mm
1.6mm
1.2mm
0.9mm
3.5mm
1 in 1000
1 in 100

12. Nasal bone

13. Tricuspid valve Doppler
Big Magnification
Apical 4-chamber
Angle < 30º
Gate: mm
Tricuspid regurgitation
Half systole
Velocity > 60 cm/s

14. Advantages of first trimester scan
To confirm pregnancy & viability
To confirm GA & Dating if needed
To confirm the number of gestational sacs, fetuses and chorionicity
To check fetal anatomy for structural anomalies
To measure nuchal translucency / screen for chromosomal abnormality
To check uterus & adnexa

15. First trimester biochemical markers
Free beta hCG
Pregnancy associated plasma protein A

16. Biochemical markers
100
Screening in the first trimester by a combination of maternal age, fetal NT, FHR and serum free ß-hCG and PAPP-A identifies about 90% of trisomy 21 pregnancies for a false positive rate of 3% NT
FHR
ß-hCG
PAPP-A
90% 90 80
ß-hCG
AFP E3 IA
71%
hCG
AFP E3 IA
67% 70
ß-hCG
AFP E3
65%
61%
ß-hCG
AFP
hCG
AFP E3
60%
hCG
AFP
56% 60
Detection rate (%) 50 40 30 20 10

17. Maternal serum free ß-hCG& PAPP-A at 11-13+6 wks20
Euploid n
2.0
In trisomy 21 pregnancies maternal serum free ß-hCG is about twice as high and PAPP-A is reduced to about half compared to chromosomally normal pregnancies.
Trisomy 21 10
0.4
1.2
2.8
3.6
4.4
4.8
Maternal serum free ß-hCG (MoM)
The performance of screening for trisomy 21 by maternal age and serum free ß-hCG and PAPP-A is:
Detection rate %
False positive rate 5% 8 n
Euploid 4
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Maternal serum PAPP-A (M0M)

18. Maternal serum free ß-hCG& PAPP-A at 11-13+6 wks
Concentration of free ß-hCG and PAPP-A is influenced by:
The machine and reagents
Gestational age
Maternal weight
Ethnicity
Smoking status
Method of conception
HyperemesisGravidarum
Twin ( Chorionicity ,vanishing)
Temperature: In first-trimester screening for aneuploidies, analysis of blood samples should be undertaken within a few minutes of collection, otherwise the samples should be refrigerated at 4 degrees C throughout the interval between collection and analysis

19. Maternal serum free ß-hCG& PAPP-A at 11-13+6 wks
In trisomy 21 pregnancies:
Free ß-hCG is higher than in euploid pregnancies and the difference between the two is higher at 13 than at 11 weeks
Serum PAPP-A is lower than in euploid pregnancies and the difference between the two is higher at 11 than at 13 weeks
The difference from euploid pregnancies in PAPP-A at 11 weeks is greater than the difference in ß-hCG at 13 weeks and therefore the overall performance of biochemical screening is better at 11 than at 13 weeks
5.0
ß-hCG
Euploid
1.0
PAPP-A
Median MoM
0.5
0.1 75 80 85 90 95
100
Gestation (days)

20. Screening for trisomy21 by fetal NT & FHR and serum free ß-hCG& PAPP-A at 11-13+6 wks
Nuchal translucency (mm) 1 2 3 4 5
Euploid
Gestation (days) 75 80 85 90 95
100
Trisomy 21
In trisomy 21 compared to euploid pregnancies:
The difference in biochemical markers is greater at 11 than at 13 weeks
The difference in fetal NT is greater at 11 than at 13 weeks
Therefore the overall performance of screening is better at 11 than at 13 weeks
5.0
ß-hCG
Euploid
1.0
PAPP-A
Median MoM
0.5
0.1
Gestation (days) 75 80 85 90 95
100

21. Screening for trisomy21 by fetal NT & FHR and serum free ß-hCG& PAPP-A at 11-13+6 wks
The overall performance of combined screening is better at 11 than at 13 weeks and may be best at 10 weeks
Ultrasound scanning for fetal abnormalities is better at 12 than at 11 weeks and much better than at 10 weeks
A good way of achieving a high performance of screening for trisomy 21 and diagnosing major fetal defects by ultrasound is to carry out the blood test at 10 or 11 weeks and the ultrasound scan at 12 weeks
Ultrasound scan at 12 wks 96 10 92 88 11
Detection rate for 3% FPR (%) 84 12 80 76
Blood test
Gestation (wks)

22. Chromosomal defects other than trisomy 21
Free ß-hCG
PAPP-A
Trisomy 18 
0.3 MoM
Trisomy 13
Turner’s 
1.0 MoM
Triploidy
 / 
0.1/10.0 MoM
0.1/1.0 MoM
Trisomy 21
2.0 MoM
0.5 MoM

23. Screening for trisomies 18 and 13 by fetal NT & FHR and serum free ß-hCG& PAPP-A at 11-13+6 wks
Trisomies 18 and 13 are the second and third most common chromosomal abnormalities after trisomy 21
.At weeks the relative prevalence of trisomies 18 and 13 to trisomy 21 are about 1 to 2.5 and 1 to 7, respectively
100 90
Trisomy 21 80
Trisomy 13
Trisomy 18 70 60
All three trisomies are associated with increased maternal age, increased fetal NT and decreased maternal serum PAPP-A
A beneficial consequence of first-trimester combined screening for trisomy 21 is the early diagnosis of trisomies 18 and 13. At a false positive rate of 3% the detection rate of trisomy 21 is 90% and of trisomies 18 and 13 is about 75% 50
Detection rate at 3% FPR (%) 40 30 20 10

24. Screening for trisomies 18 and 13 by fetal NT & FHR and serum free ß-hCG& PAPP-A at 11-13+6 wks
There are differences between the three trisomies:
Fetal NT is higher in trisomies 18 and 13 than in trisomy 21
Serum PAPP-A is lower in trisomies 18 and 13 than in trisomy 21
Serum free ß-hCG in trisomy 21 is high whereas in trisomies 18 and 13 this is low
Fetal heart rate in trisomy 13, unlike trisomies 21 and 18, is high
The use of specific algorithms for trisomy 18 and trisomy 13, in addition to the use of the algorithm for trisomy 21, improves the detection of trisomies 18 and 13 from about 75% to 95% with a minor increase in the total false positive rate from 3% to 3.1% 10 20 30 40 50 60 70 80 90
100
Detection rate at 3% FPR (%)
Trisomy 21
Trisomy 18
Trisomy 13

25. Selected strategies for screening
Depends on:
Availability of screening test
Availability of well trained and certified sonographer
Availability of good equipped Laboratory with well trained technician and Lab. Team
Cost
Availability of diagnostic test
Low false positive

26. Screening strategies NT 1st Trimester 64-70 79-84 90-95 60-69 67-81
Strategy
Analytes
Detection rate (%)
1st Trimester NT
64-70
NT+ PAPP-A, hCG or free beta-hCG
79-84
NT+ PAPP-A, hCG or free beta-hCG + New markers
90-95
2nd Trimester, Triple test
MSAFp, hCG or free l3-hCG, uE3
60-69
2nd trimester , Quadruple (Quad) test
MSAFp, hCG or free l3-hCG, uE3, inhibin
67-81

27. A screen-positive test result indicates that the woman's risk of having a child with Down syndrome is equal to, or exceeds, a specific cut-off level This cut-off level is program/laboratory-specific and based on the combination of markers used, among other factors. A typical cut-off for the combined test is the term risk of Down syndrome of ≥1 in This is associated with a false positive rate (FPR) of about 5 percent (eg, about 5 per 100 women will have risks higher than 1 in 300 – such as 1 in 250 or 1 in 75). The odds of Down syndrome in this group of women is about 1 in 20 (eg, for every 20 women screen-positive, 1 will have a Down syndrome fetus and 19 will have a normal fetus)

28. First-trimester combined and stepwise sequential testing should not be offered if CVS is unavailable . Alternatively, they may choose to undergo secondary screening using a maternal plasma-based test for cell free DNA. Although not diagnostic, the high sensitivity and specificity of the DNA test will reassure many of these women that their risk of having a Down syndrome pregnancy is very low, which allows them to avoid the risk associated with an invasive diagnostic test. Among those women with a positive DNA test, the risk of Down syndrome is increased, but still requires confirmation by an invasive diagnostic test (eg, amniocentesis to obtain amniocytes for karyotyping).

30. Screen-negative first-trimester or integrated test results — A negative test result means the patient's risk of having a baby with Down syndrome is less than a specified cut-off level; it does not exclude the possibility of Down syndrome. The patient's risk is usually provided in the report (eg, Down syndrome risk 1 in 9000) and this number can be given to the patient with a discussion of its meaning. With regard to Down syndrome screening, no further testing is recommended.

31. Conclusion
Screening for chromosomal defects should be offered to all pregnant ladies who attend at < 20 weeks
Proper counselling must be done with parents
Screening strategy must be chosen accordning to:
Gestational age
Available certified sonographer
Availabe certified Laboratory
Affordable cost
Risk and counselling after result must be done accurately by physician NOT Laboratory or even sonographer unless sonographer is perinatalogist
The final decision must be from parents not the physician which is possible if counselling is effective.

32. …Conclusion NT is the best marker As a single marker IF…
Combination of NT with biochemistry will increase the detection rate and may decrease false positive rate
Training programs for sonographers ( www. Fetalmedicine.com)
Increase the number of certified Laboratory with proper softwares , machines and trained technician)
Establish multicenter studies to find out our normal ranges ( MoMs)