Reproductive Implantation Failure


By Mark Perloe, M.D.

[A note from the author: I hope in this article, and the recorded webinar,  introduces concepts that must be considered when evaluating reproductive implantation failure (RIF) and help you become a better informed participant in your care. There is a long history of interventions that initially appeared to be beneficial that, after further testing in well-designed studies, failed to prove beneficial.]

Our introduction to RIF is complicated by many factors. The first of which, is the lack of consensus on a definition. Early studies defined RIF by the total number of day three embryos transferred (10-12 embryos). After a myriad of advances in IVF technology, more recent studies define RIF as failure after  3-4 good quality blastocysts (or euploid CGH tested blastocysts)  have been transferred.

We are in the age of evidence-based medicine and decisions should be based on the best available evidence. When such evidence is available, we must remember that well-designed studies with sufficient sample size are difficult to fund and complete. As a result, authors resort to meta-analysis where the results of multiple studies are statistically combined to come to a conclusion about the effectiveness of a given intervention. This way of analyzing data assumes a one-size-fits-all approach to medicine rather than looking at each woman as an individual. We must remember that lack of good quality evidence is proof that the appropriate studies are incomplete, instead of attributing the treatment ineffective. Our approach is to consider whether there is evidence to support a treatment benefit and that the proposed intervention is safe. We consider alternative treatments in the existing literature that may better support our decisions. We also reflect on the whether the cost of the intervention is reasonable. 

The failure of embryos to implant is linked to a number of different variations:

  • Abnormal embryos,
  • Embryo transfer technique,
  • Problems with the “host uterus,”
  • Problems with interaction between the embryo and uterus or multiple factors.


Embryo evaluation includes:

  • Looking at morphology,
  • Time-lapse video,
  • Mitochondrial analysis,
  • Follicular fluid analysis,
  • Analysis of spent embryo culture media protein or metabolites, and
  • Genetic screening (array CGH blastocyst screening or NextGen sequencing).

There is little pregnancy outcome data supporting the routine use of any of these techniques to evaluate the embryo save for aCGH blastocyst genetic screening.

Time lapse embryo monitoring has been shown to predict blastocyst morphology using algorithms based on embryo cleavage on the first and second day of embryo growth. This is a lack of data as to whether this increases implantation compared to blastocyst morphology or array CGH. Future studies looking at earlier transfer based on this data may allow for improved results.

Augment mitochondrial transfer is a new technique with only two published abstracts. The data is insufficient to suggest this technology plays a role in patients with implantation failure.

Embryo transfer techniques are standardized with optimal results using a soft catheter, ultrasound guidance and transferring in the mid endometrial cavity. The use of assisted hatching seems to be of benefit after embryo cryopreservation or select cases only. Data is insufficient to recommend use of embryo glue (hyaluron media supplementation).

Anatomical factors within the host uterus may adversely affect implantation. Anatomical factors such as uterine leiomyoma, adenomyosis, Asherman’s syndrome (intrauterine adhesions), thin endometrium, surgical history and the presence of hydrosalpinx may interfere with development of the endometrium, endometrial blood supply and a normal uterine micro-contraction pattern. Hormonal or metabolic disorders such as insulin resistance, uncontrolled diabetes, thyroid disease or elevated prolactin levels may adversely affect pregnancy initiation and outcome. Obesity may affect both embryo quality and implantation.  Infection can also block implantation. The expression of various biochemical markers such as integrins, mucin 1, calcitonin, leukemia inhibitory factor, cyclo-oxygenase and HOXA10 have all been evaluated and found lacking as useful clinically useful tools to affect IVF pregnancy outcome.

The endometrial gene expression pattern in 238 genes assessed by microarray (ERA) has recently been introduced to pinpoint the optimal implantation window. In women with three previous failed ovum donation cycles, an in phase ERA resulted in a 62.8% pregnancy rate and a 38% implantation rate. Of those tested, biopsies were in phase 73.7% while 26.3% were non-receptive. Non-receptive biopsies were corrected in 88% of women when embryo transfer was performed after one or two additional days of progesterone. While this data is promising, we lack information about the prevalence of non-receptive biopsies in women who achieve successful pregnancies. Nor did the study include a control group where the biopsy was performed and the researchers were blinded to the results to prove treatment benefit.

Recent studies have shown no correlation of any immune- related testing , including women with elevated anti-thyroid antibodies or ANA, NK cells, NK activation, HLA typing and IVF pregnancy in an unscreened population. Other studies reveal that implantation rates are the same whether women had high levels, low levels or undetectable amounts of anti-phospholipid antibodies.

While there is sufficient data to suggest that uterine NK cells play an important role in implantation, research to date has been unable to link specific test results with embryo implantation failure or pregnancy outcome.  This difficulty is due to limited sample size, the lack of the appropriate control population, different test methodology or other study design issues.

Furthermore, there is little correlation when comparing the cytotoxicity of uterine NK and circulating NK cells.  Uterine NK cell profiles ascertained by endometrial biopsy vary depending on the biopsy technique and location in the endometrial cavity as well as with each day after ovulation.  Markedly different results are noted when measuring circulating NK cells that can vary based on changing estrogen levels across the menstrual cycle.

Kalu demonstrated a Th1 bias at the time of oocyte retrieval in women with RIF compared to women with a successful pregnancy. In the latter group, the converse was noted. [Kalu AmJReprodImmunol 2008]

Th1 cytokine-mediated infertility was explored in studies that suggest benefit with Anti-TNFalpha therapy. [Clark, JReprodImmunol 2010].

Liang reported higher Th1:Th2 ratios in women who failed to conceive with IVF compared to successful pregnancies as well as in women with RIF. A drop in this ratio across the stimulation cycle was seen with successful pregnancy and a higher Th1:Th2 ratio was seen only on the day of hCG administration in RIF patients. [Liang, AmJReprodImmunol 2015].

Elevated preconception CD56+ 16+ and/or Th1:Th2 levels predict benefit from IVIG therapy in sub fertile women undergoing IVF. [Winger, AmJRperodImmunol 2011].

Polanski found only three studies that evaluated the use of adjuvant immunotherapy in patients undergoing IVF where the evaluation of NK cells were considered. While improvements were seen leading to 63% improvement in clinical pregnancies, individual studies lacked statistical power, demonstrated marked heterogeneity data presentation [per patient vs per cycle], use of different medications and dosage regimens suggest a cautious approach to applying this data. [Polanski HumReprod 2014].

THERAPEUTIC APPROACHES [ text in italics indicates possible effective interventions]

Measures prior to embryo transfer

  • Restore uterine environment: hydrosalpinges, endometrial polyps, leiomyoma
  • Mock ET
  • Endometrial injury performed in cycles prior to ET
  • Blastocyst biopsy and array-CGH or NextGen sequencing
  • Lifestyle modification, weight loss & stress reduction
  • Embryo cryopreservation with elevated estradiol or progesterone levels
  • No benefit to routine antiphospholipid antibody testing, ANA  or antithyroid AB
  • Time-lapse morphometric analysis
  • Augment mitochondrial transfer
  • Assisted hatching
  • Acupuncture
  • Endometrial Receptivity Assay
  • Th1:Th2 cytokine testing
  • NK activity
  • Immunological adjuvants: IVIG, Intralipid, Neupogen, Methylprednisolone, Heparin/Lovenox


Measures during embryo transfer

  • Ultrasound guided transfer
  • Type of catheter
  • Depth of catheter placement
  • Embryo glue as the transfer medium
  • Oxytocin inhibitors

Measures after embryo transfer

  • Progesterone supplementation: IM or vaginal administration equally effective. Oral progesterone supplementation is not effective
  • Progesterone supplementation FET: IM or combination IM/Vaginal may offer an advantage vaginal route
  • No Bedrest


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