Due to variation in definition of implantation failure there is no accurate data available for Incidence or prevalence of RIF. RIF is unidentified and its sensitivity is analysed between 5-25%.
Maternal age plays a crucial role in quality of embryos that are used in IVF cycle. With Increase in Maternal age frequency of aneuploidy also increases. Pregnancy rate also decreases with increased age.
BMI also impacts implantation so in obese patient there is high chance of implantation failure as compared with patient of normal weight.
Cigarette toxins play role in disrupting corpus lute formation and also affect embryo implantation.
Stress leads to release of cortisol production in body which is called stress hormone and leads to greater chance of miscarriage.
RIF is determined when transferred embryos fail to implant following several IVF cycles. For successful implantation we need a receptive endometrium and a normal healthy embryo (blastocyst) and a synchronized dialogue between embryo and endometrium.
The cross talk between endometrium and embryo finally leads to apposition, attachment and invasion of embryo that is required for successful pregnancy.
This process involves many hormones or mediators originating from embryo , endometrium and also maternal immunological system.
Any abnormality in endometrium, Embryo or Immunological system will result in failure.
I)GAMETE AND EMBRYO FACTOR
Embryo quality is very important for successful implantation. Quality of embryo depends upon oocyte and sperm quality.
Oocyte quality is very important as it forms majority of volume for Embryo. Compromised oocyte quality can be seen when yield is in two extreme I.e. too high or too low.
Advanced maternal age, high FSH ,low AFC and low AMH is associated with poor response. Maternal age is related with increased chromosome non disjunction, aneuploidy, increased mitochondrial damage and decreased in mitochondrial membrane potential is noted.
Sperm quality is equally important to achieve fertilisation , good embryo quality and implantation. Sperm DNA Damage should be evaluated by DFI.
UTERINE FACTORS can lead to RIF
It can lead to distortion of endometrial lining and distorted uterine contractility. It leads to altered uterine vascular perfusion and increased uterine natural killer cells.
Leads to mechanical interference with embryo transfer and implantation.
It leads to disturbed Endo Myometrial junction which leads to altered uterine vascular perfusion, progesterone resistance and alteration in PR-A and PR-B ratio.
This prevents embryo from attaching to luminal surface of endometrium and so it impairs endometriums receptivity by reducing progesterone receptors and increase risk of miscarriage.
Thin endometrium can be associated with low pregnancy rate. Uterine linning has two layers , functional layer which is shed with menstruation and basal layer which persists. Functional layer has plenty of small blood vessels and basal layer has large spiral arteries. When ovulation occurs there is constriction of spiral arteries with reduced blood flow to functional layer. This results in reduced oxygen tension which is good for implantation of embryo.
When the endometrium is thin or less than 7mm it is the functional layer which is thin or absent and embryo will be closer to basal layer and spiral arteries and higher vascularity and oxygen concentration of basal endometrium, which affects implantation.
Various cytokines are involved in implantation . Local dysregulatin of normal expression or action of cytokines can cause implantation failure.
Elevated natural killer cells , dysregulation of interleukins (IL) 12,15,18 and high IL-1Beta and low interferon and IL-10 were found in RIF.
There is also increase level of aromatase p450 mRNA , changes in pinopode expression and high matrix metalloproteinases are associated with RIF.
Three main player of immune system for implantation are
Natural Killer Cells
There are two broad classes of T Helper lymphocytes TH1 and TH2.
TH1 cytokines which include interferon , tumor necrosis factor, interleukins IL 1,2,12,15,18
TH1 cytokines are counteracted by TH2 cytokines which are IL4,5,6,10,13 and granulocyte macrophage stimulating hormone.
In pregnancy there is a shift towards TH2 dominance which is required for maintenance of pregnancy.
In early pregnancy following changes are seen ,there is rise in levels of progesterone, there is increased secretion of TH2 cytokines like IL4 and 6 and there is decreased secretion go TH1 cytokines like IL 2,12 and interferon.
Sometimes its said that embryonic gestation & RPL are related to loss of TH2 dominance.
Natural Killer Cells
There are two type of natural killer cells peripheral and uterine. There are no such reports of evidence of association between NK cells and pregnancy outcome.
Another aspect of immune system altering endometrial receptivity is related to autoimmunity. At present association between autoimmunity and ART remains in conclusive.
Before puberty vaginal flora is a mixture of both aerobic and anaerobic bacteria while after puberty vagina is colonised predominantly by lactobacilli species which is due to acidic environment created by rising glycogen.
There are studies which suggest that non lactobacilli dominant microbiota correlated with adverse reproductive outcome like RIF Miscarriage.
It causes Impaired Fertilisation and causes altered folliculogenesis.
It can also result in poor oocyte quality.
It can result in altered folliculogenesis and defective ovulation. It can also lead to inadequate progesterone action , excessive androgen insulin action and sometimes poor oocyte quality.
Because of hydrosalphinx there is intermittent bathing of endometrium lining with hydrosalphinx fluid can cause interference to apposition. There is Embryotoxic effect of inflammatory hydrosalphinx fluid.
Assessment of oocyte quality and quantity through ovarian function test Patients with RIF are offered basal FSH. AFC and AMH to diagnose extremities of ovarian reserve which is generally associated with poor oocyte quality.
Studies have shown that DFI more than 27% is associated with pregnancy failure in ART.
Incidence of chromosomal Abnormality in couple with RIF is approximately 2.5%, which higher compared to general population. So karyotype should be considered in RIF.
Time lapse Imaging
Comprehensive chromosome screening
Women with RIF should be investigated for uterine pathology which can be a cause for RIF. Hysteroscopy and laparoscopy, sonohysterography and 3D USG are the investigation that can be used as diagnostic tool.
Testing TH1 & TH2 balance and imbalance are pregnancy is associated with TH2 dominance.
It is not known whether the the transition of TH2 dominance in poor pregnancy outcome is effect or cause.
So no screening tests can be done in advance to predict TH1/TH2 imbalance.
Testing of NK Cells can kill some cells in vitro but not directly. Routine testing of NK cells in women with RIF is not advised as there is no clear evidence of use. Testig for autoantibodies should be done.
Success of IVF cycles is the collaboration between the embryo and the endometrium which decides success or failure.
There are two causes for RIF one is displaced WOI or pathologically disrupted WOI.
It is clearly seen that in natural process the endometrium becomes receptive after 8-10 days of ovulation.
ERA is customised microarray performed by next generation sequencing coupled with computation predictor which enables to identify the receptivity of endometrial sample i.e. whether the endometrium is within the time frame of WOI or not, thus providing personalised WOI of a given patient facilitating personalised embryo transfer.
A biopsy of endometrium tissue is taken at day LH + 7 days in a natural cycle and progesterone +5 in HRT Cycle.
A state of non receptivity proves that WOI is displaced.
Thus ERA can identify the patient will need personalised WOI or not especially in case of RIF.
Multidisciplinary team should be there which should compromise of reproductive medicine specialist, embryologist, geneticist, immunological and endocrinologist.Couple with RIF should be evaluated by team.
In few patients RIF might be because of compremised oocyte quality and this could be because of inherent problems in oocyte quality or because of suboptimal ovarian stimulation which can be corrected.
It reduces oxidative stress on sperm
Reduces number of sperms with increased DFI
Morphologically selected sperms may improve reproductive outcome
Sperm DNA damage is lower in seminiferous tubules as compared with caudal epididymis and ejaculated sperms
-laser assisted hatching
-preimplantation genetic testing for aneuploidy
-time lapse imaging &Metabolomics
4)IMPROVING EMBRYO TRANSFER
-Ultrasound guided transfer should be done
-use of embryo glue and adherent compound
-Freeze all strategy should be done
Operative Hysteroscopy and septal resection . It causes increased implantation rate and decreased miscarriage rate and increased term delivery rate.
Hysteroscopic polypectomy as it improves pregnancy rate
SUBMUCOSAL & IMTRAMURAL FIBROID PROTRUDING IN ENDOMETRIAL CAVITY
Myomectomy ca be done as it improves implantation rate and decreases miscarriage rate ,CPR,LBR.
Depot Gnrha alone or in combination with cytoreduction surgery. Gnrha causes regression of Adenomyoma by hypogonadotropin status as it acts on type 1 and 2 receptors on endometrioum.
Cytoreduction surgery reduces hypertrophy and subsequently improves function by bringing uterine layer closer . It also enhances blood supply.
Repair the impaired linking ,restoring normal uterine cavity and fertility. Adhesiolysis permits endomterium to establish its anatomy and fuction.
A) ENDOCRINE STRATEGY
-High dose estradiol
-G-CSF can be used
B) VITAMIN &SUPPLEMENTS
-Vitamin E plus pentoxifyline
3) SURGICAL STRATEGY
It mends the intrauterine envoirnment by acting as immunomodulator and reduces uterine natural killer cells count and stabilises cytokine expression in endometrium and decreases Endometrium inflammation.
Reduction of inflammation in uterine cavity and improvement of uterine and ovarian perfusion which improves endometrial receptivity and and ovarian responsiveness.
It enables invasive phenotype of thromboblast. It also increases insulin like growth factor which increases trophoblast invasion.
4) INTRAVENOUS IMMUNOGLOBULIN
It reduces cytotoxic natural killer cells and enhancement of regulatory T cells and downregulation of antibody producing cells.
It decreases peripheral natural killer cells actively and suppression of pro inflammatory cytokines.
Administration of Gnrh antagonist for 3-6 months before ART in women with endometriosis significantly improves pregnancy rate. Surgery can also be done but it does affect ovarian reserve upto some extent.
2) TREATMENT OF HYDROSALPHINX
-Laproscopic proximal tubal occlusion
-USG guided drainage of hydrosalphinx fluid can be done(but there is risk re accumulation and also risk of introducing infections higher)
If implantation fails to occur in spite of repeated treatment attempts or prognosis is poor alternative treatment option should be given.
If problem lies with embryo gamete donation is recommended.
If problem lies in uterus surrogacy must be discussed.