(1) Background: During IVF (in vitro fertilization) procedures, endometrial thickness has a significant role in the success of pregnancy outcomes for embryo transfers. Endometrial thickness, a crucial component of endometrial receptivity, is a contentious issue. The regenerative properties of PRP have been shown in recent research to have positive effects on the endometrium. PRP increases the pregnancy rate in IVF patients with thin endometrium and recurrent implantation failure. In order to demonstrate the efficacy of PRP therapies, this work compares the administration of injectable and infusible PRP during endometrial preparation. (2) Methods: This prospective single-arm control study was conducted at an IVF center in Oradea, Romania. This study included 50 patients; 27 were included in the group with Injectable PRP and 23 in the group with Infusible PRP. The outcome was compared between the two groups, with the primary outcome being the endometrial thickness after the PRP infusion or injection and the secondary outcome being the pregnancy rate in both groups. (3) Results: Patients who were treated with Injectable PRP had a higher pregnancy rate. An improvement in the quality of the endometrium, in terms of thickness, was also observed in the patients who were injected with PRP. (4) Conclusions: Compared to PRP infusions inside the uterus, sub-endometrial PRP injections in frozen embryo transfer methods have a greater pregnancy rate.

Background and Objectives: Recurrent implantation failure (RIF) affects 10% of couples undergoing in vitro fertilization (IVF), spurring exploration into tailored treatments to enhance implantation rates. Maternal immune tolerance towards embryos, particularly killer-cell immunoglobulin-like receptors (KIRs) on natural killer (NK) cells, is a focal point in RIF research. Materials and Methods: This retrospective cohort study, conducted at fertility clinic in Oradea, Romania, involved 65 infertile couples undergoing IVF treatment between January 2022 and December 2023. Couples were divided into two groups: KIR AA (Group A) and KIR Bx (Group B). Results: Factors such as age, type of infertility, oocytes retrieved, embryos produced, pregnancy rates in Group A without and with immunomodulatory treatment were documented. Group A, receiving immunomodulatory treatment, achieved a pregnancy rate of 47.8%, significantly higher than the 23.73% rate without treatment (p = 0.008). Group B had a higher mean patient age than Group A. However, miscarriage rates did not significantly differ between Group A with treatment and Group B (p = 0.2457), suggesting comparable outcomes with immunomodulation. Conclusions: The impact of immunological factors on recurrent implantation failure is being more and more emphasized and warrants the attention of specialists in human reproduction. Uterine natural killers and their function though KIR receptors deserve particular attention as immunomodulatory treatment may improve pregnancy rates in patients with KIR AA haplotype.