**6. Conclusion**

*Innovations in Assisted Reproduction Technology*

ultrasounds and serum hormone level measurements.

endometrial thickness does play a vital role in receptivity (**Table 1**).

The patient populations presented in these studies, including those among the study group and those in the control group, were all patients that had suffered two or more failed previous cycles due to poor lining development. The inclusion criteria for these studies were consistent through all eight trials and provided an unbiased patient group in order to obtain reliable results. The data conclusively shows that endometrial thickness among patients with chronically poor endometrial development is greatly increased with PRP infusion therapy in comparison to traditional HRT alone. The primary outcome of each study was satisfied by the significant increase in endometrial lining development with the secondary satisfaction of improved clinical pregnancy outcomes in the PRP group versus the control group. Another diagnostic tool to be considered in patients with a history of suboptimal endometrial development and repeat implantation failure is the use of the Endometrial Receptivity Array (ERA). The ERA is a customized array that allows to test for 248 different genes expressed during the endometrial cycle and works concordantly with a computational algorithm that identifies the receptivity status of an endometrial biopsy to diagnose a personalized window of implantation [28]. ERA is performed with a mock embryo transfer cycle. Utilizing the ERA, Ruiz-Alonso and colleagues were able to validate conclusively that 25% of RIF patients had a displaced window of implantation and went on to coin the phrase "personalized embryo transfer" (pET) to increase the chance of a successful pregnancy in women suffering from mistimed endometrial receptivity [29]. Potentially, ERA can be utilized in conjunction with PRP infusion to determine receptivity of the endometrium in PRP patients. In the study by Tandulwadkar et al. [21], not only was lining thickness assessed, but endometrial vascularity was observed as well utilizing 3D Doppler ultrasound. Blood flow to the endometrium as well as the uterine biophysical profile can be measured via a combination between abdominal and transvaginal ultrasound. Greater blood flow to the uterus has been associated with higher implantation rates and can be seen in color utilizing Doppler ultrasound methods [27]. PRP infusion has the potential to increase lining development as well

endometrial lining should be at the forefront of clinical researchers within the ART industry. Platelet-rich plasma is easily attained, cost-effective, minimally invasive, rich in cytokines and growth factors, and carries very little risk of disease or infection transmission as the patient uses their own blood to attain PRP. Infusion into the endometrium takes place in conjunction with traditional HRT and therefore can be administered during the average cycle while patients are already present for serial

In the eight studies discussed above, PRP infusion into the endometrium proved effective when administered on various days of an HRT cycle as well as in variable quantities. While the majority of studies reviewed were clinical applications, which presents a weakness in the data as there was no comparative control group, the randomized controlled trials that were performed offered arguably conclusive, supportive evidence of PRP effectiveness. All the patients that underwent PRP infusion experienced a significantly marked increase in endometrial thickness, allowing for frozen embryo transfer. In the studies that did utilize a study population versus a control population, results among the study participants were significantly improved with greater cycle completion. Although most studies utilized frozen blastocyst transfers, there were some that elected to use frozen cleavage stage embryo transfers, which can also be considered a limiting factor among the data. The studies here agreed upon 7 mm as the minimal lining thickness for embryo implantation success, but some physicians argue that endometrial thickness is a poor marker for transfer outcome. While this argument can be made and supported, as it was by Griesinger and colleagues [11], there is a wide consensus that

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The review of the initial data presented in these eight early studies of PRP infusion into the endometrium in conjunction with traditional HRT reveals statistically significant outcomes. Patients with previous failures that did not reach the minimal lining thickness needed to perform embryo transfer (>7 mm) underwent PRP infusion into the endometrium and reached an average endometrial thickness of 7.36 mm in comparison to the control group, which reached an average of only 6.77 mm. Clinical pregnancy rates within the study group were also significantly higher than the control group, 50% (108/216) versus 17.1% (16/93), respectively. For patients that have had multiple failures and canceled cycles, offering an absolute solution that at minimum guarantees them an embryo transfer can potentially increase the success of frozen embryo transfers in clinics globally, while decreasing patient stress and costs, and reducing the potential for embryo wastage.
