clinical results after the use of CGH, blastocyst biopsy and vitrification: implantation improves from 28% to 67% (p<0.0003) and delivery rate from 60% to 80%.

1. Comprehensive chromosomal screening at the
blastocyst stage
Dagan Wells, PhD, FRCPath
dagan.wells@obs-gyn.ox.ac.uk

2. Limitations of conventional embryo screening techniques
Cells are in interphase - use FISH
Limited range of fluorochromes
Less than half the chromosomes tested
Spreading requires skill and can be inconsistent
Mosaicism Poses a significant problem for diagnosis.
However, most mosaic cleavage stage
embryos are aneuploid in every cell.
Cleavage stage biopsy may represent a cost to the
embryo

3. Comparative genomic hybridization- CGH
• Technique related to FISH
• Allows the copy number of every chromosome to be determined
Chromosome 15
Test DNA Normal DNA
Normal Trisomy
Loss Monosomy
Gain
Normal
Kallioniemi et al 1992;
Wells et al 1999, 2002; Voullaire et al 1999; Wilton et al 2001; Gutierrez et al 2004, 2005; Fragouli et al 2006, 2007

4. Embryo screening using CGH
Benefits
• All chromosomes tested
• DNA-based
• No spreading of cells on slides
But what about mosaicism and the impact of biopsy?

5. Comprehensive chromosome screening of blastocysts
Trophectoderm biopsy-
3-10 cells (mean 5) biopsied and tested
Courtesy of M. Katz-Jaffe and J. Stevens, CCRM

6. Comprehensive chromosome screening of blastocysts
Analysis of blastocyst stage
• Biopsy of several cells is possible
Diagnosis more robust and accurate
Less risk of misdiagnosis due to mosaicism
Reduced impact of embryo biopsy
• Blastocyst cryopreservation (vitrification) necessary
• Can overcoming the principal challenges to accurate screening
allow PGS to fulfill the potential predicted by theory?

7. Blastocyst CGH- clinical results
• 170 patients, mean age 38 years, 1-6 previous failed IVF cycles
(mean 2)
• Near 100% survival after biopsy, freeze and thaw
• Pregnancy rate per cycle with transfer 87% 72%
• Birth rate per cycle with transfer 79% 60%
• Implantation rate per embryo 67% 28% *
Control group matched for: maternal age, day-3 FSH, day of transfer, # oocytes
retrieved, # of failed cycles
*p<0.0003 - Extremely promising for single embryo transfer

8. Blastocyst CGH- rates of pregnancy loss
• Embryo loss rates are low
• 91% of embryos that produced a fetal sac resulted in an
ongoing third trimester pregnancy or live birth
• 97% of embryos that produced a fetal heart beat resulted in an
ongoing third trimester pregnancy or live birth
• Expected pregnancy loss rate for IVF patients in this age
range is ~25%

9. Blastocyst CGH- Pregnancy rates
100
90
80
70
Positive pregnancy
60 per transfer
50
40 Positive pregnancy
per cycle with biopsy
30
20
10
0
30-34 35-38 39-42 43-50
Pregnancy rate per transfer shows only a small decline with advancing age
Pregnancy rate per cycle shows a significant decline

10. Blastocyst CGH- aneuploidy and implantation rates
Why does age still lead to reduced pregnancy rates despite aneuploidy
screening?
100
90
80 Implantation rate
70
60
Aneuploidy rate
50
40
30 Cycles with all embryos
aneuploid
20
10
0
30-34 35-38 39-42 43-50

11. Conclusions
• Pregnancy rates were above those typically achieved for all age
groups.
• However, pregnancy rates were lower for older patients due to
the increased frequency of cycles with no euploid embryos.
• Chromosomally normal embryos from older patients have a
similar chance of producing a child as those derived from
young patients.
• Aneuploidy is likely to be the principal factor causing reduced
IVF success with advancing maternal age
• Spontaneous abortion rates were reduced for all
patients, including those with a history of multiple miscarriage

12. Questions
• Can the results obtained in the current study be replicated in a
randomized controlled trial?
• An RCT is currently underway
• What patient groups will benefit the most from this type of
screening?
• Young patients may benefit, particularly in countries where
single embryo transfer is mandatory

13. United Kingdom (Oxford) Colorado Center for
Elpida Fragouli Reproductive Medicine
Samer Alfarawati
Mandy Katz-Jaffe
John Stevens
United States (Livingston, NJ) Bill Schoolcraft
Pere Colls
Tomas Escudero
N-neka Esprit-Ngachou
Jill Fischer
Cristina Gutierrez-Mateo
Santiago Munne
Renata Prates
Jorge Sanchez
Sophia Tormasi
John Zheng
Dagan.Wells@obs-gyn.ox.ac.uk