Dr. Priya Chittawar discusses the challenges and complexities of implantation in IVF, noting that 60% of cycles don't result in pregnancy despite improved techniques. Key factors affecting implantation include the quality of embryos, endometrial receptivity, and hormonal interactions, with a significant portion of conceptus lost before implantation. Future advancements may focus on better assessment of endometrial conditions and potential gene therapies to enhance implantation success rates.

1. The Enigma of
Implantation

2. Dr. Priya Chittawar
Associate Professor and Head of Unit
Mohak Laparoscopy and Infertility Center
Sri Aurobindo Institute of Medical Sciences
Indore

3. Natural Cycle

4. IVF

5. The Patients Perspective
 Egg+ Sperm= Baby
 Surprised to learn that 60% of the ivf cycles don’t
end in a pregnancy
 What went wrong?

6. What Went Wrong?
 The follicles did not develop as expected?
 The oocyte|sperm quality was not so good?
 The fertilization rate was suboptimal?
 The embryo quality on morphology was not good?
 The embryo transfer was difficult?
 The endometrial development was suboptimal?

7.  Even after an ivf cycle in which everything
apparently goes well, after transfer of apparently
good quality 3 embryos the pregnancy rates are
around 30 to 40 %
 Pregnancies are known after transfer of poor quality
single embryo.

8.  Is the fertility and implantation in human beings
naturally low ?
 Monthly fecundity rate in a normal couple is 20 to
25%
 Is the low implantation rates in ART cycles due to
an altered physiological state?

9.  Almost 30 to 70% of conceptus are lost before or at
the time of implantation.
 We have improved almost all aspects of ivf: ovarian
stimulation, embryo culture and transfer but
pregnancy rates hover around 30 to 40%
 The bottleneck is the process of implantation.

10. The Bottleneck!

11. Average pregnancy rate of 50% cannot be further
increased by the improvement of embryo transfer and
culture conditions or by optimal selection of
blastocysts
The endometrial function and endometrial receptivity
have been accepted to be major limiting factors in the
establishment of pregnancy.

12. Implantation
The process by which the embryo attaches to the
uterine wall and first penetrates the epithelium and
then the circulatory system of the mother to form the
placenta.
Most vital and the least understood part of
reproduction

13.  Implantation begins 2-3days after the fertilized egg
enters the uterus on day 18-19 of the cycle, 5 to 7 days
after fertilization.
 Hormone dependent changes in the four compartments
of the endometrium
1. Glandular epithelium
2. Luminal epithelium
3. Stroma
4. Resident immune cells ( NK cells)

14. Successful implantation
 Embryo at the blastocyst stage
 Endometrium in the short spanned ‘implantation
window’
 Successful cross talk between the two

15. Implantation
 Apposition
 Adhesion
 Invasion

16. Apposition
Progressively increasing contact between trophoblast
and uterine epithelium by
1.Decrease in uterine fluid volume
2.Edema of the endometrium
3.Enlargement of the embryo

17. The Implantation Window

18. Pinopodes

19.  Pinopodes are surface epithelial microvilli that
exhibit cystic changes
 They appear in normal cycles from day 20-22 and in
stimulated cycle from 18-22
 They live for 48 hours
 Presumably reduce the uterine fluid volume and
facilitate intimate contact between blastocyst and
uterine epithelium

20.  Pinopods are visible on conventional histology as
bulbous protrusions of the cell apices
 Histology is performed on tissue sections where
only a small area of the surface can be examined
 Scanning Electron Microscopy is most appropriate
to study pinopod formation
 Mirrors serum progesterone concentration.

21.  Because of the need for invasive biopsy, pinopod
determination cannot be done in treatment cycles

22.  The interactions between fertilized egg and the
endometrium is determined by the interplay of
hormones estrogen and progesterone
 There bind to intracellular receptors and the
resulting proteins upregulate or downregulate
genes which influence implantation

23. Up- and down-regulated factors of the proliferative and secretory phase.
Strowitzki T et al. Hum. Reprod. Update 2006;12:617-630
© The Author 2006. Published by Oxford University Press on behalf of the European Society of
Human Reproduction and Embryology. All rights reserved. For Permissions, please email:
journals.permissions@oxfordjournals.org

24.  There is loosening of epithelial cell to cell contacts
during pinopod formation which may facilitate
invasion
 In endometrial epithelial cells growing on stromal
cells in vitro, human blastocysts adhered only to
areas bearing the pinopods

25. Adhesion
 Expression of extracellular matrix components
occurs in the endometrium which helps adhesion of
the blastocyst to the endometrium
 Alpha five beta four integrin , leukemia inhibiting
factor and insulin like growth factor.

26. Invasion
1. Trobhoblastic cells invade between the uterine
epithelial cells on their path to basment membrane
2. Epithelial cells lift off the basement membranes,
allowing the trophoblast to insinuate underneath
the epithelium
3. Fusion of trophoblast with uterine epithelial cells.

27. Implantation in IVF cycles
 Embryos transferred on day 2/day 3/day5
 The embryos are transferred transcervically with
some amount of culture media
 Endometrial development is accelerated due to high
concentrations of steroids
 Culture conditions may speed up or retard
embryonic development

28. Estrogen Levels in IVF

29. Seed or Soil?

30.  Select the best ‘seed’
 Prepare the soil
 Plant at the appropriate time

31. Improving implantation…
 Improving embryo quality
Better ovarian stimulation, good lab performance,
extended culture
 Better way to choose the embryos for transfer
 Be wary of multiple pregnancies

33. BESST IVF OUTCOME
 BESST: Birth of a successful singleton at term
 Avoid multiple births in IVF
 Improving implantation is vital to achieving this
goal.

35. Improving Implantation

36. Problems in assessing
Endometrium
 Complex interaction of biomarkers
 In vivo studies are done in non conception cycles as
invasive sampling is needed
 Gene suppression experiments provide only indirect
evidence about the role of the the resulting
biomarker

37. What Tomorrow Holds
 Better assessment of endometrial receptivity using
integrin and pinopode assessment
 Study of endometrial secretions by microdialysis for
glycodelin and other biomarkers
 Assessment of endometrial gene expression and
 Therapeutic applications of HOX 10 gene by gene
therapy to improve implantation

38. What Tomorrow Holds
 Optimizing implantation will increase pregnancy
rates
 Evaluation of implantation biomarkers will help
predict pregnancy outcome and detect occult
implantation defects
 Gene therapy targeted at genes responsible for
implantation will give a new therapeutic option
 Manipulating the expression of key implantaton
genes by surgical medical or future gene therapy
will help improve implantation rates

40. Thank You!