Ryttg

1. PREIMPLANTATION
GENETIC TESTING
BY/ SAMEH IBRAHIM

2. Contents
 Overview:
- Definition - Hypothesis
-Ethical consideration - PGT and PND
 TYPE
 Indication
 Techniques :
1- biopsy type
2- genetic analysis
 Recommendations

3. Definition
• PGT: An early form of prenatal genetic diagnosis( formerly
known as PGD)
• A test performed to analyze the DNA from oocytes or
embryo for (HLA)-typing or for determining genetic
abnormalities. These include:
• PGT-A PGT-M PGT-SR

4. PGT
Hypothesis:
1-Alternative to conventional PND to stop the need to
terminate an affected on-going pregnancy.
2- increase the success of infertility treatment.
3- As away to enable single embryo transfer(SET).

5. Ethical considerations
• PGT : Controversial procedure as some fell it is unethical
to select embryos on their genetic or chromosomal
analysis.
• PGT is not allowed in some countries, such as Germany
which do allow PND and TOP.
• PGT for family balancing is not legal practice in some
countries.

6. Differences between PND and PGT
PND PGT
Genetic diagnosis Genetic diagnosis
During pregnancy Before pregnancy
TOP : if fetus affected Avoid TOP
If embryo affected no transfer
If embryo unaffected may be
pregnancy
Need for IVF

7. Types
• PGT-A: for aneuploidy screening( formerly PGS).
• PGT-M: For monogenic/ single gene defects (formerly
single gene PGD).
• PGT-SR: for chromosomal structural rearrangements
(formerly chromosomal PGD).

8. Types
• The goal of PGT-M is to establish pregnancy that is
unaffected by specific genetic characteristics, such as a
known heritable genetic mutation carried by one or both
biological parents.

9. Types
• The goal of PGT-SR is to establish pregnancy that is
unaffected by structural chromosomal abnormality
(translocation) in couple with translocation or deletion.

10. Types
• The goal of PGT-A is to identify embryos with aneuploidy,
in couples presumed to be chromosomally normal.

11. Indications
• PGD( PGT-M, PGT-SR)
• PGD is the testing of embryos for specific genetic
abnormalities known to exist in one or both parents.

12. Indications
• Candidates for PGT-M
1- Couples known to be at increased risk of offspring with a
specific single gene disorders
(eg, cystic fibrosis, sickle cell disease, Duchene muscular
dystrophy, hemophilia, spinal muscular atrophy)
2- Couples who wish to give birth to a child with a
compatible HLA type for stem cell therapy of sibling( savior
sibling).

13. Indications
• 3- couples who wish to a avoid a sex linked disorder in
offspring
• 4- The use of PGT-M for mitochondrial disorders
• 5-Select embryos at risk for inherited cancer syndromes
which included hereditary breast and ovarian cancer
(BRCA1,BRCA2), LI Fraumeni syndrome (LFD1) and
familial adenomatous polyposis

14. Indications
• Controversial
• Sex selection for purposes family balancing.
• HLA matching for the purposes of creating a tissue donor
for an existing diseased sibling.

15. Indications
Candidates for PGT-SR:
• Couple with translocation at risk of recurrent pregnancy
loss from balanced/ unbalanced translocation.
• 4% of couple experiencing recurrent pregnancy loss will
have one partner with an identifiable balanced
translocation as a potential cause of the loss.

16. Indications
• Candidates for PGT-A
• A screening test for embryos resulting from parents with
normal karyotype
There is insufficient evidence of efficacy
IVF adjuvant and its use is controversial

17. Indications
 Indications:
- Advanced maternal age.
- -Repeated implantation failure
- Recurrent pregnancy loss
- Sever male factor
- Improve embryo selection in eSET cycles.

18. Indications

19. Technique
• 1- Biopsy type .
• 2- Genetic analysis.

20. Technique

21. Biopsy type:
1- Polar body biopsy
2- cleavage stage biopsy
3- Blastocyst biopsy

22. Biopsy type:
• 1- polar body biopsy
- Genetic composition of oocyte
- The polar body can be removed simultaneously or
sequentially.

23. Biopsy type:
Advantages:
- Can be performed soon after oocyte retrieval
- Result can be available within two days and so fresh ET
can be applied.
- No apparent effect on FR or embryo development.
- Potentially less invasiveas pbs do not make physical
contribution to the embryo.

24. Biopsy type:
• Disadvantages :
• Detect maternal errors only
• The oocyte must either be fertilized or cryopreserved
before the results of PBB are available.

25. Biopsy type:
• PBB may diagnosis a meiotic aneuploidy after meiosis l
that goes to self correct after meiosis ll
• Costly; why(10 EGG= 20 TEST)
• Time consuming to the embryology team.

26. Biopsy type:
• PBB IS least used technique due to less predictive of
reproductive potential than other approaches.
• PGT-A performed with the PBB will not increase live birth
rates.(ESHRE.2018)

27. Biopsy type:
2-Cleavage stage biopsy:
 Day 3 cleavage stage.
 1-2 blastomeres from the 6-8 cell embryo.
 Method of zone drilling:
-Acid Tyrodes -laser

28. Biopsy type:
• Advantages:
Sampled from the embryo it self
More representative of its chromosomal content.

29. Biopsy type:
• Disadvantages:
- Limited to one or two cells
- -Mosaicism( up to 50%).
- Can negatively affect embryo viability and implantation
potential.

30. Biopsy type:
• 3- Blastocyst biopsy:
- Day 5-6 after fertilization.
- The blastocyst contains more than 100 cell.
- Method to obtain genetic material :
laser acid Tyrodes Sharpened glass needle.
- 5 to 8 cells are removed from trophectoderm.

31. • Advantages:
-No adverse impact on embryo Implantation potential
-Less mosaic , chance of embryo self correction
compared to day 3 biopsy
-More cells to analyses diagnosis more
accurate.
-Fewer embryo to analyses more cheaper.
-Blastocyst transfer is a method of embryo selection in
itself, as almost half of embryo will not develop to the
blastocyst stage.

32. Disadvantages :
-Limitations to fresh embryo transfer.
- Chromosomal make-up of the trophoectoderm my not be
representative of the inner cell mass in up to 35% of
cases.
- Mosaicism is also present.

33. The test procedures
1- fluorescence in situ hybridization (FISH)
analysis that utilized selected chromosomes. Most evidence with
this method did not show improvement in IVF outcomes.
Not used today
2-Now CCS (Comprehensive Chromosome screening)
performed on 24 chromosomes.
Option include:
-CGH -SNP array
-PCR - NGS

34. The test procedures
• WITH 24 Chromosomes analysis, evidence for PGT-A is
more mixed. A few (RCT) comparing elective single
embryo (eSET)of euploid embryos determined by PGT-A
versus morphology grad based selection of embryo found
non inferior or improved pregnancy rates amongst the PGT-
A group.
• A 2011-2012 retrospective data analysis from national ART
database found a possible increase in LBR in woman aged
> 37 who utilize PGT-A.

35. • Morphological evaluation remains the gold standard and
most commonly used method for embryo selection.
• Transfer of good morphology embryo not always mean
good quality embryo.

36. PGD VS PGS

37. Recommendations
• Routine application of PGT‐A in patients with advanced
maternal age, recurrent implantation failure or good
prognosis is not supported by current evidence.
• PGT‐A may reduce the time to pregnancy and the risk of
miscarriage, but significant improvement in live‐birth rate
has not been demonstrated.
• Improvement in techniques used to carry out PGT may
lead to a change in recommendation when new evidence
is available.

38. Recommendations
• Live birth rate with mosaic embryos has been shown to
reach up to 50% in some studies, hence when no euploid
embryos are present consideration of transferring
embryos with the lowest mosaicism rate could be
discussed and considered.
• Transferring all embryos obtained from one cycle
one‐at‐a‐time is expected to give as good as, if not better,
chances of a live birth than with screening.

39. Thank you