1) PGD and PGS are genetic testing techniques used prior to embryo transfer in IVF treatment. PGD screens for known genetic disorders while PGS screens for chromosome abnormalities. 2) While PGD has clear benefits when used appropriately, the effectiveness of routine PGS is questionable as it may reduce pregnancy rates. Techniques like day 3 biopsy have limitations due to mosaicism. 3) Extensive counseling is important given technical limitations and risks of erroneous results. Not all genetic issues can be detected and treatment has biological limits. Caution is needed against unnecessary "indication creep".

1. PGD – The good, bad and
ugly
Dr Aniruddha Malpani, MD
www.drmalpani.com

2. Questions
• What is the difference between PGD
and PGS ?
• Should we be doing PGD for
everyone ?
• Does PGD help ? Or harm ?

3. Will this embryo become a
baby ?

4. Pre-implantation Genetic Diagnosis
• Handyside, Winston, and Hughes
• 1990 for sexing embryos for preventing X
linked disorder
– Used PCR for Y chromosome and transferred XX
embryos
• Definition: Biopsy of a single cell per embryo,
followed by its genetic diagnosis through
different techniques (FISH, PCR, aCGH, NGS ),
and the subsequent transfer of those embryos
classified as genetically normal

5. PGD vs PGS
• Preimplantation Genetic Diagnosis (PGD)
• Refers to diagnosis of a definitive genetic
condition in an embryo
• AIM: To provide disease free offspring
• Preimplantation Genetic Screening (PGS)
• Refers to screening of embryos for known
genetic defects (mainly chromosome
aneuploidies)
• Aim: To improve the IVF outcome

6. Indications
PGD
• Single gene disorders
– Thalassemia, DMD,
• Carriers of chromosome
abnormalities
– Translocation carriers
PGS
• At risk for aneuploidy
– maternal age > 35 yrs
– Prior trisomic conception
• Recurrent pregnancy losses
• Failed IVF cycles
– >3 prior embryo transfers with
high quality, morphologically
normal embryos

7. PGS – old vs PGS – new
Polar body: Not recommended by ESHRE
Day 3 . Blastomere
Disadvantages
- Chance of damaging the embryo
- Only single cell sampled
- MOSAICISM
- Embryo is alive – autocorrection of genetic abnormalities
Advantages
- Permits collection of many cells
Day 5 . Blastocyst

8. Techniques to choose for
PGD/PGS
Depends on the disorder !
• Chromosomal
• FISH
• Array CGH
• SNP array
• NGS
• Molecular (those that require PCR)
• PCR- Sequencing
• PCR variants
• NGS

9. Problem : Mosaicism
• Not all the cells of a given embryo are
genotypically identical
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Y
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46X
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47X
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Simple mosaicism Chaotic
10-25 % of embryos are mosaics
Cause of misdiagnosis

10. Solution: Trophectoderm biopsy (Blastocyst stage)
• Advantages
– More accurate. Permits collection of
more than 2 cells
– Reduces risk of misdiagnosis because of
mosaicism
– Reduces number of embryos to be screened
• Disadvantages
– Need to freeze embryos and then transfer
them in the next cycle after thawing
– May not get enough blastocysts to biopsy,
especially in the older woman

11. PGS cannot diagnose all genetic
problems – only what you look
for !

12. Words of caution
• Counseling is a very crucial component of PGD/PGS
• Patients understand the
• risk for having an affected child
• the impact of the disease
• the multiple technical limitations including the possibility of an erroneous
result
• Discuss alternative options, including the use of donor
eggs and adoption
• Prenatal Diagnosis of patients undergoing PGD (not
required for PGS)
• Field of genetics advances rapidly. Need to work closely
with the embryologist and the geneticist

13. The embryo is alive !
• Embryo has the amazing ability to
self-correct and repair itself
• Abnormal cells die by apoptosis
• They are eliminated and replaced by
healthy cells, repairing - and in
many cases completely fixing - the
embryo.

14. Mouse model of chromosome
mosaicism reveals lineage-specific
depletion of aneuploid cells and
normal developmental potential
• Helen Bolton, et al
• Nature Communications . Published 29
March 2016

15. Limitations
• Miscarriages can occur after transfer of “
normal “ PGS tested embryos .
• Time-consuming and expensive.
• Lots of coordination and expertise. Best
offered in a few referral centers
• Large number of embryos may be abnormal,
thus leaving few or no healthy embryos for
transfer. Older patients produce few
embryos. PGS can actually reduce pregnancy
rates

16. The American Society for Reproductive
Medicine (2007) position on PGS
• Available evidence does NOT support the use
of PGS as currently performed :
• to improve live-birth rates in patients with
advanced maternal age ( AMA)
• to improve live-birth rates in patients with
previous implantation failures ( RIF).
• to improve live-birth rates in patients with
recurrent pregnancy loss ( RPL) .
• to reduce miscarriage rates in patients with
recurrent pregnancy loss related to aneuploidy

17. PGS for aneuploidy
(Schattman, UptoDate review, 2014)
• “PGS using day 3 blastomere biopsy and FISH decreases the
chances of live birth.
• In couples with recurrent pregnancy loss, PGS is unlikely to
benefit those with proven karyotypically normal
miscarriages.
• In patients with karyotypically abnormal miscarriages, PGS
may decrease the risk of subsequent miscarriage, although
there is no evidence that it will increase the probability of
having a child.
• In young, good prognosis couples, PGS using blastocyst biopsy
and 23 chromosome analysis may improve the chance of
conception with single embryo transfer; however, the chance
of live birth after including frozen embryo transfers is not

18. An adverse past and an
uncertain future
• In 2007, Mastenbroek et al. published a RCT (n=206 patients in PGS and
n=202 in the control group for older women.
• PGS (day 3 biopsy + fluorescence in situ-hybridization-FISH) reduced the
rates of ongoing pregnancies and live births (PGS = 24%; Control = 35%).
This was the first time in which the use of PGS was criticized.
• Advocates of PGS blamed negative outcomes on:
• imperfect FISH technique
• biopsy carried out on the third day (embryo cleavage stage) would carry
a high frequency of mosaicism.
• Solution = PGS-new . Biopsy on Day 5/6 !
• Use new genetic techniques (Comparative genomic hybridization-CGH;
Array-CGH-aCGH; Real-time quantitative polymerase chain-reaction-
qPCR; Next generation sequencing-NGS)

19. New wine in old bottles ?
• Poor quality biased RCTs
• Selects good prognosis patients only !
• Restricted to special populations (a
mean of 16 eggs collected and 6
blastocysts produced) Rare in the
universe of older patients who require
ART.

20. Indication creep
• Good example – ICSI
Do it now for all IVF patients.
However a bad IVF lab can kills lots more
eggs when doing ICSI as compared to doing
IVF !
• When you invest all that time, money and
expertise in learning how to do PGD, what do
you do with that expertise if there aren’t
enough patients? The answer is simple -
create more patients !

21. Routine PGS for all IVF patients
• Why not do PGS for all older women ? Makes logical
sense
• Next step - Why not just offer it to everyone who is
doing IVF ?
• Which patient is going to want genetically abnormal
embryos transferred?
• If you are spending so much for IVF, why not spend a
little more ?
• However, in real life , we forget that all these
additional technical procedures add to risk; cost, and
time

22. Why PGS has become “ hot”
• World leading clinics present their data at conferences
Other IVF clinics want to start copying them
• Patients demand this “new “ technique which reporters
write about
• IVF doctors like doing new stuff ; especially when this
increases our income
• PGD was supposed to revolutionise IVF treatment and
improve pregnancy rates. Ended up reducing pregnancy
rates for patients who never needed it in the first place.
• Steep learning curve with technically complex procedures
• Patients serve as uninformed guinea pigs in these clinics.

23. Medical reversal = more is not
always better
• Too much technology can cause unintended harm
• IVF doctors don’t seem to learn. Repeat the same mistakes
every decade.
• “New “ set of technologies come with the promise that they
are better!
• IVF treatment has a limited success rate. Human
reproduction has its own biological limitations.
• Papers published in medical journals quote high success
rates. This can be very misleading . Most IVF clinics can
never match those rates because they simply don't have the
experience or expertise of these researchers.