This document discusses evaluating the success of preimplantation genetic screening (PGS). It notes that early randomized trials of PGS found poorer outcomes compared to controls, likely due to technical limitations at the time like poor biopsy techniques and limited screening. More recent studies using day 5 biopsy and comprehensive chromosome screening are finding improved implantation and pregnancy rates with PGS. However, for PGS to be successful, all steps from egg retrieval to embryo transfer must be optimized. Outcomes also depend on patient factors, and PGS may not help all clinics or patients. The key measures of success are changes in implantation and pregnancy rates that exceed expected outcomes without PGS.

1. How to evaluate success with PGS
Don Leigh
ASPIRE April 2014

2. IVF . . . What can be done to improve things?
• ~2/3 of clinical miscarriages are caused by chromosome aneuploidy
• Some aneuploidies are not observed in miscarriages and believed to be
implantation/development lethal
• IVF implantation rates decrease with increasing age
• IVF embryos show variable aneuploidy rates (5-70% age related)
• Natural pregnancies show an age related increase in incidence of trisomy 21
PGS should provide an opportunity to improve the success of an embryo transfer
 Transfers have emotional, time and monetary costs
 Implantation failures and miscarriages have high emotional cost, larger time costs, health costs and
significant monetary costs
It is a logical conclusion that identifying and avoiding the
transfer of aneuploid embryos will change the implantation
rates and also the miscarriage rates

3. Why the question about PGS efficacy?
Randomised Trials
• Sizes: 60-~400 patients
• Biopsy stage: 8x blastomere (1/2 cells), 1x blastocyst
• Prognosis group: AMA (5), Good (3), RIF (1)
• Outcomes
 Implantation rates: Control 7%-60% Test 14%-56%
 Miscarriage rates: Control 4%-38% Test 20%-70%
Mastenbroek et al 2011

4. What did PGS offer?
• Aneuploid embryos were identified and excluded but
most results were poorer
The simplest conclusion was that PGS is in fact detrimental
to transfer outcomes . . .!!
X
X
X
X

5. PGS back then . . . . .
• ESHRE data XI
 Implantation rate: 13%-35% ave. 22%
 Miscarriage rate: 6%-39% ave. 16%
• Polar Body (RGI)
 Implantation rate: ~32%
 Miscarriage rate: decreased
• Literature
 Implantation rate: 20%-35%
 Miscarriage rate: <10%
FISH- 5c, 7c, 9c

6. The arguments back then . . .
• Poor Biopsy technique
 Poor biopsy technique damages the embryo
– 1 blastomere- development stage sometimes not appropriate
– 2 blastomeres- reported already as detrimental
• Poor analysis
 Poor technique
– High analysis failure rate indicative of poor lab practices
 Wrong screening set used
– 5-9 chromosomes tested- but these are not the most prevalent
aneuploidies observed in embryos (35-60% coverage)
• Mosaicism
 Cleavage stage embryos often mosaic. Wrong identification and
exclusion. Loss of good cells leaving poorer embryo. Rejection of good
embryos

7. A laboratory process can have a major impact on success
• Polar Body
 Technically the most challenging (good technique essential)
 Debate on whether it is inclusive enough to identify sufficient
aneuploidies
• Day 3
 Mosaicism may be relevant (but realistically how relevant?)
 Some technical challenges (good technique important)
• Day 5
 Need extended culture (not difficult in a good lab)
 Technically straight forward
 Time needed for analysis- freezing?

8. A breakthrough . . .?
• Wells et al 2008
 Implantation failure patients
 Day 5 trophectoderm biopsy
 Vitrified embryos
 CGH 24 chromosome screen
Finally . .
 Total chromosome screen
 Implantation rates approached 70%

9. PGS now . . . .
• Now all gross chromosome abnormalities were
identifiable- including those aneuploidies leading to
implantation failure and miscarriage
 typically 40% to 70% of embryos are aneuploid and should not be
used
• Now more and more studies report similar positive
implantation rate changes after PGS
• But Wells’ group also did
 D5 biopsy
 Frozen cycles
Were these the important differences?

10. Stage of biopsy . . . .
60%
50%
40%
30%
20%
10%
0%
day 3 biopsy day 5 biopsy
control
biopsy
Treff et al 2011
Screening must improve outcomes
>60% just to overcome impact of
biopsy

11. To measure Success- the interested parties . . .
• Patient
• Clinician
• Laboratory
• Clinic (Finance, marketing, . . . )

12. Success- for the patient
• Patients come to the clinic for many reasons
– Subfertility
 Implantation failure, miscarriage
– Advanced maternal age
– Monogene disorder/translocation
– Recurrent miscarriage
• patients just want a pregnancy
– A continuing pregnancy
 This will not be achieved for some patients
– Actually, the patient actually wants a baby
 A healthy baby
– Possibly babies- healthy babies- this will not be achieved for a significant number
of patients

13. Success- for the clinician
• Good stimulation
– Good eggs (cannot get a good embryo from a bad egg)
Good embryos
–A transfer (uterine receptivity)
»A pregnancy
• A healthy baby
• A happy patient

14. Success- for the Lab
•Need good eggs
–Good embryos (fert*, culture*)
Biopsy*/analysis*
–Transfer (or freeze*)
»Pregnancy
•Healthy baby

15. The caveats . . . .
PGS does not make any embryo better- it is only a tool to facilitate
embryo choice to avoid a significant source of biological negatives
• At best, the laboratory maintains the vitality of an embryo . . . or in
a poorly operating clinic makes it worse
• PGS does not improve the patient factors (eg uterine receptivity)
• PGS should not be thought of as the best way to improve a clinic’s
outcomes
 Implantation rate is a key lab performance indicator- general fresh and frozen
implantation rates show how a clinic is performing
 In some cases, lab improvements may be the best approach to give the
improvements that a clinic is after (Beyer et al 2008)

16. PGS can be a positive
Performed correctly, PGS
• Improves implantation rates for some (most?) patients
– Decreases the futile transfers for most patient types (young,
AMA, recurrent implantation failure*, miscarriage*, tl) by
avoiding transfer of unfit embryos
• Decreases miscarriage rates
– Minimises miscarriage especially for AMA and tl carriers (but
only aneuploid related miscarriages)
• Can offer single embryo transfer cycles as a real option
– Without losing pregnancy rates
– Double embryo transfers and the risks associated with multiple
gestations can be a thing of the past

17. What limits successful application of PGS?
-ve factors
• Poor stimulation
• Poor embryology- biopsied embryos show greater
sensitivity to lab conditions
• Biopsy- poor technique has greater negative impact
• Biopsy timing- different costs at different stages
• Poor freezing (fresh = frozen)
• Analysis- poor analysis loses good embryos
• Transfer- fresh vs frozen
– Uterine receptivity and state, embryo/uterus synchronicity

18. Other considerations
• Successful pregnancy is a +/- outcome
– PGS only changes the approach to this outcome.
• Some patients will not achieve a pregnancy
– Not with their own eggs (sperm)
– Not with anyone’s embryos
• Everything we do to an embryo has a negative
impact- some big, some small

19. Will PGS offer all clinics success?
PGS does work in the right situations- previous failures to show
improvements were likely a combination of too many
negatives with insufficient positives. Current failures may
point to clinic failures
Biopsy may have a larger negative impact on outcome than the
positive gain of excluding aneuploid embryos
Different patient groups will see different levels of improvement
after PGS- but most will see something
• Some clinics should possibly not be attempting PGS until they
improve general lab outcomes

20. The final measure of success . . . .
When the result/outcome >>
original likely outcome
This will occur with PGS when all of the steps from
egg through embryo through analysis through
transfer/storage are all appropriate and optimal

21. PGS and its limits
• PGS offers assistance in identifying the best starting
point- it only changes implantation rate
– Current form of PGS will improve
 More detail ?more improvement in IR?
BUT
• Without better understanding of the patient variables as
well, then the approach to a 100% outcome will stall
In the future Preimplantation screening will include both
embryo status and patient variables

22. Thank you

23. The Patient
• Typically limited exposure to IVF
– Primary or secondary infertility
• Often reason for sub-fertility not known
– Male factor, female factor, neither, both
• Maybe has tried IVF
– Implantation failure
– Sub-clinical miscarriages
• Age risk of Down syndrome
– Only a few aneuploid syndromes identified- other aneuploidies
result in implantation failure or early loss
• Clinical use- chromosome rearrangements
• New type of patient – fertile but a miscarriage history

24. The clinician
Cannot get a good embryo from a bad egg
• Compromised maturation
 Other factors (Stimulation type, trigger, etc)
 Aneuploidy?
• Number of eggs
 Low quality? Age related decline in recruitment (AMH)
• Age related aneuploidy increase
 Base line may reach 60-70% (more if translocation involved)

25. Success for the lab
• Egg quality
 Delivered (Bad eggs, bad embryos)
• Fertilisation
 Male factors, lab skills
• Culture conditions
 Impact of compromised laboratory conditions on growth and
development
• Transfer timing
 Embryo stage
 Patient receptivity