Prenatal diagnosis

1. PRENATAL DIAGNOSTIC
TECHNIQUES

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

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

15. PRENATAL RISK FACTORS
 Oligohydramnios
 Polyhydramnios
 Severe symmetrical IUGR
 Abnormal USG findings

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)

19. PROCEDURE OF TRANSCERVICAL

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

24. PROCEDURE

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.

27. TRANSVAGINAL CVS
INDICATIONS:
-Uterine retroversion
-Myomas
-Placental localization

28.  Chorionic villus is obtained by transvaginal
aspiration under guidance with an endovaginal
probe.

29. LABORATORY ASPECTS OF CVS
 Direct cytogenetic analysis
 Long term tissue culture

30. COMPLICATIONS
 Fetal loss(1-2%)
 Oromandibular limb deformities
 Vaginal bleeding
 Limb reduction deformity

31. False positive results (2-3%) - placental mosaics
and maternal cell contamination

32. AMNIOCENTESIS
DEF:
Deliberate puncture of the amniotic fluid sac per
abdomen

33.  Carried out as an op procedure.
 Early:11-14 , Late: 14-16
 Proper counselling.
 USG examination.

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.

37. ADVANTAGES
 Degree of accuracy
 Degree of hemolytic process in the fetus

38.  Disadvantages:
-Pregnancy loss
-Amniotic fluid leekage
-Fetal trauma

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

41. CORDOCENTESIS

42. USES:
 Fetal abnormalities detected by USG.
 Fetal growth retardation
 Polyhydramnios
 Hereditary defeciences of other haemostatic
system
 Hemoglobinopathies
 Metabolic disorders.

43. ADVANTAGES
 High quality karyotype in 48-72 hrs rather than 10-
14 days that is needed for amniotic tissue culture.
 Vein is larger in size.

44. COMPLICATIONS
 Bleeding from the puncture site(30%)
 Fetal bradycardia(5%)

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

51. GENETIC TESTS
 Cytogenetic analysis
 Fluorescence in situ hybridization
 Southern blotting
 Polymerase chain reaction
 Linkage analysis
 Chromosomal micro array analysis

52. CYTOGENETIC ANALYSIS

53. FLUOROSCENCE IN SITU HYBRIDISATION

54. SOUTHERN BLOTTING

55. TYPES OF CHROMOSOMAL ABNORMALITIES
 Numerical
- trisomy
- monosomy
 Structural- deletions/duplications/ translocations
Chromosomal
abnormality
Genetic syndrome Incidence per
10000 births
Trisomy 21 Down 15
Trisomy 18 Edward 3
Trisomy 13 Patau 2
Monosomy X Turner 2(female)
XXY Klinefelter 10(male)

56.  Translocation- reciprocal
robertsonian
 inversions – pericentric
paracentric

57. .