In recent years, platelet-rich plasma (PRP) has emerged as a promising alternative for treating endometrial pathologies that affect the endometrial lining. Several studies have tested this therapeutic approach in human patients, but the results are inconclusive. Moreover, in recent years, different investigations have suggested that PRP derived from umbilical cord blood (hUC-PRP) contains a higher concentration of growth factors and other pro-regenerative molecules than PRP obtained from adult peripheral blood. In our previous pilot study conducted in 15 patients with endometrial atrophy/Asherman syndrome/thin endometrium, preliminary results indicate that hysteroscopic injection of hUC-PRP increases endometrial thickness and improves the endometrial pattern. For this reason, the present study aims to corroborate our previous findings by increasing the number of patients to 35, in prior HRT cycles in these women, to gain a deeper understanding of the effectiveness of this new therapy.