aim of that study is to compare the effect between autologous intrauterine Platelet-Rich Plasma instillation and three snip hysteroscopic endometrial scratching for thinned endometrium.

Embryo implantation is a very delicate and well-orchestrated process that is governed by the interaction between several maternal and embryonic factors, ultimately resulting in adherence of the blastocyst to the endometrium. For a short period of time during the normal menstrual cycle, the endometrium represents the fertile "soil" for the implanting embryo. The human endometrium undergoes complex changes, in response to circulating estrogen and progesterone, which culminate at the mid-luteal phase of the menstrual cycle when it becomes suitable to host the blastocyst.

In clinical practice, a thin endometrium, unresponsive to conventional therapies, usually results in cycle cancellation and embryo cryopreservation. The evaluation of an adequate endometrial growth is performed using grey-scale ultrasound. The minimal endometrial thickness required for embryo transfer is now considered about 7 mm at the end of natural or medically induced follicular phase Local injury to the endometrium has been proposed as a means to improve implantation in women with RIF. Initial non-randomized studies showed a doubling of implantation rates after 2-4 endometrial injuries performed at different time points of the menstrual cycle in women with previous implantation failure . Following that, a number of randomized trials focusing on women with RIF have been conducted. The majority of the trials have demonstrated significant improvements in implantation rates, clinical pregnancy rates and/or live birth rates following endometrial injury performed in the preceding cycle Platelet rich plasma (PRP) represents a relatively new approach in regenerative medicine. It is obtained from patient's own blood and contains different growth factors and other biomolecules necessary for wound healing. Platelet rich plasma (PRP) therapy has accumulated considerable attention over the two last decades, mainly due to its potential ability in regenerative medicine. Platelets as a main components of the PRP, contain more than 1100 different proteins, with numerous post-translational modifications, resulting in over 1500 protein-based bioactive factors These factors include immune system messengers, growth factors, enzymes and their inhibitors and factors which can participate in tissue repair and wound healing. Another important characteristic of PRP is that represents an autologous product, which is prepared from the patient's own blood. Therefore, the use of autologous PRP eliminates any concerns about the risk of crossed contamination, disease transmission or immune reactions

Inclusion Criteria:

Endometrial thickness < 7 mm under estrogen replacement therapy or repeated implantation failure Age between 18 and 38years

Exclusion Criteria:

Age < 18 and > 46 years Pregnancy Bleeding diathesis Previous uterine surgery (miomectomy, cesarean section, etc...) Platelet count < 105/μL Hemoglobin < 10 g/dL Presence of a tumor in the wound bed or metastatic disease Current diagnosis of cancer Other concomitant active infections Other factors of infertility ( PCO, tubal block, congenital anomalies, genetic malformation, male infertility)

female