2. FIRST TRIMESTER SCREENING
11- 13+6 weeks
CRL of 45- 84mm.
Maternal age
Nuchal translucency
Maternal serum beta hCG
Maternal serum PAPP-A level
Additional ultrasound markers
3. Maternal age
Trisomy 13,18 ,21- ↑ses with maternal age
detection rate ↑ to 75-80%(maternal age+ NT)
Nuchal translucency
maximum thickness of subcutaneous translucent area
between skin and soft tissue overlying fetal spine at the back
of neck.
CRL 38- 84mm
4. NUCHALTRANSLUCENCY
Mid sagittal view
Head in neutral position in
line with spine
Fetal neck skin
differentiated from amnion
by fetal movt
Widest part should be
measured
Callipers should be placed
in inner border of white line
5. BIOCHEMICAL MARKERS IN FIRST TRIMESTER
beta hCG and PAPP-A
Beta hCG MoM
normal 1
Trisomy 21 2
Trisomy 18 0.2
Trisomy 13 0.5
PAPP-A MoM
Normal 1
Trisomy 21 0.5
Trisomy 18 0.2
Trisomy 13 0.3
Beta hCG is lower in women who are HIV positive
6. ADDITIONAL FIRST TRIMESTER ULTRASOUND MARKERS
1. Nasal bone
2. Reversed a wave in ductus venosus
3. Tricuspid regurgitation
4. Wide fronto maxillary fascial angle
7.
8. COMBINED FIRST TRIMESTER SCREENING
NT+ β Hcg +PAPP-A
79-87%
Maternal age affects first trimestic aneuploidy scan
<35years :- 67-75%
>35years :- 90-95%
9. SECOND TRIMESTER SCREENING
Between15 and 21 weeks of gestation
Detailed ultrasound scan
Maternal serum beta hCG
Maternal serum AFP
Maternal serum uE3 level
Maternal serum inhibin A level
10. Beta hCG- peaks at 15 wks→ gradually falls at17-22wks
Trisomy 21- increased in both trimesters
Alpha fetoprotein- produced by liver and gastrointestinal
tract of fetus
- marker of open spina bifida
- Trisomy 21 ↓ by 25%
Free Estriol- Trisomy 21 ↓ by 25%
Inhibin A- ↑ to 1.77 MoM in trisomy 21
11. COMBINED FIRST AND SECOND TRIMESTER
SCREENING
Integrated screening
NT+ serum analytes at 11 to 14 weeks+ quadruple
markers at 15 to 20 weeks
Highest Down syndrome detection rate( 94-96%)
Sequential screening
stepwise sequential screening
contingent sequential screening
12. CELL FREE FETAL DNA SCREENING
Non invasive prenatal screening
Not recommended for multiple gestation
High specificity and sensitivity for trisomy 18 and 21
Doesnot assess risk of fetal anomalies such as neural tube defects
or ventral wall defects
Recommended for women >35 yrs
usg findings of increased risk of aneuploidy
H/O trisomy affected offspring
positive first or second trimester screening result
parent wth balanced robertsonian translocation
ACOG 2015
13. GENETIC COUNSELING
3% of newborns have major congenital anomalies.
Etiologic factors:
1. Chromosomal abnormalities
2. Single gene disorders
3. Polygenic or multifactorial disorders
4. Teratogenic disorders due to exposure of
exogenous factors
14. MATERNAL RISK FACTORS
Maternal age > 35 years
Family history of neural tube defects
Previous baby born with neural tube defect
Previous child with chromosomal anomaly
One or both parents – carriers of sex linked or
autosomal traits
One parent is known to carry a balanced
translocation
History of recurrent miscarriage
16. Uncontrolled diabetes mellitus in the
periconceptional period
Contact with infection
Presence of soft tissue markers
Abnormal maternal serum screening
17. INVASIVE PROCEDURE FOR PRENATAL
DIAGNOSIS
Chorionic villus sampling
Amniocentesis
Cordocentesis or percutaneous umbilical blood
sampling
18. CHORIONIC VILLUS SAMPLING
Diagnosed by italian biologist Giuseppe simoni,
1983
Diagnosis of genetic disorders
3 approaches:
Transcervically-10wks to 13 wks
Transabdominally-10wks to term
Transvaginal(rare)
20. ADVANTAGES OF TRANSCERVICAL
CVS
Genetic diagnosis is achieved at an early
gestational age.
Comfortable to the patient
Technically simple.
21. DISADVANTAGES
High risk of fetal loss than traditional amniocentesis
Chromosome composition & enzyme composition
of the chorionic villus is ocassionally different from
the fetal cells
Difficult if the placenta is above the lower one third
of the uterus
22. CONTRAINDICATIONS
-Positive neisseria gonorrhoea culture of the cervix
-Active genital herpes
-Active bleeding
-Maternal coagulopathy
-Cervical stenosis
-Severe cervicitis
-Uterine myomas
-IUD inside the pregnant uterus.
23. TRANSABDOMINAL CVS
It certainally reduces the potential risk of infection
when compared to vaginal procedure.
Two techniques
-Single needle
-Two needle
25. ADVANTAGES OF TRANSABDOMINAL
CVS
Minimal risk of infection
It does not cause vaginal bleeding
Performed in the second and third trimester.
26. DISADVANTAGES
Amount of tissue obtained is less than that with
transcervical cvs.
Patient discomfort is more.
Difficult to perform if placenta is posterior.
33. Carried out as an op procedure.
Early:11-14 , Late: 14-16
Proper counselling.
USG examination.
34.
35. Main risk factors:
-Rh isoimmunization in Rh negative mothers.
-Infection
36. Other risks:
-Changes with the gestational age
-Preprocedure or concominant use of the USG.
-Size of the needle
-Number of needle insertions
-Characteristics of the amniotic fluid
-Experience & ability of the indivudual performance.
39. PRECAUTIONS
Prior sonographic localisation of placenta is
desirable to prevent bloody tap and fetomaternal
bleeding
Prophylatic administration of 100mg of anti-D
immunoglobulin in Rh-negative nonimmunized
mother.
40. CORDOCENTESIS
Described in 1983 by Fernand Daffos.
Procedure to obtain fetal blood.
INDICATIONS:
-Fetal transmission of toxoplasmosis
-Rapid karyotype of the fetus with anatomic
deformities
-Chromosomal abnormalities
45. CVS
AMNIOCENETESI
S
CORDOCENTESIS
TIME Transcervical 10-
13wks,
Transadominal 10
weeks to term
After 15
weeks(early 12-14
weeks)
18-20 weeks
MATERIALS FOR
STUDY
Trophoblast cells Fetal fibroblasts
Fluid for
biochemical study
Fetal white blood
cells(others-infection
and biochemical study)
KARYOTYPE
RESULT
Direct preparation:
24-48 hrs
Culture: 10-14
days
Culture:3-4weeks 24-48hrs
FETAL LOSS 0.5-1% 0.5% 1-2%
ACCURACY Accurate Highly accurate Highly accurate
TERMINATION OF
PREGNANCY
1st trimester-safe 2nd trimester-risky 2nd trimester-risky
46. HISTORY
Introduced initially in 1990, at
Hammersmith Hospital,
London
By Handyside .
Combines advances in
molecular genetics & ART
47. PGD INDICATIONS
Procedure is offered to couples:
With known genetic disorders
- autosomal recessive
- autosomal dominant
- x linked disorders
- triplet repeat disorders
requesting sex selection for X-
linked disorders
Chromosomal abnormalities
48. PGD INDICATIONS
The procedure has also been offered to couples:
undergoing IVF at risk for aneuploidy
maternal age > 35 years
Prior trisomic conception
with recurrent pregnancy losses
Prior failed IVF cycles (>3 prior embryo transfers
with high quality, morphologically normal embryos)
Requesting PGD for HLA-typing (to allow selection
of embryos that are histocompatible with live
siblings)
Requesting sex selection for “family balancing”
Cancer predisposition syndromes.
49. PRECONCEPTIONAL PRENATAL DIAGNOSTIC
TECHNIQUES ACT(PC PNDT)
Why this act ?
. Prohibition of sex selection
. Detection of genetic abnormalities/
metabolic disorders/ chromosomal
abnormalities/ congenital malformations/ sex
linked disorders
. Prevention of sex determination leading to
female feticide
50. Genetic counseling centre- a gynecologist or a
pediatrician having 6 months experience/ 4wks
experience in genetic counseling/ a medical
geneticists
Genetic laboratory- a medical geneticist/ a lab
technician having 1 yr experience in conducting
prenatal diagnostic procedures
Genetic clinic/ ultrasound clinic
gynecologist having experience of performing at
least 20 procedures
a sonologist/ imaging specialist/ registered
medical practitioner/ medical geneticists
