Thin Endometrial Lining

The goal of this clinical trial is to evaluate if engineered mechanically umbilical cord-derived stem cell exosomes, or conventional umbilical cord -derived stem cell exosomes, can improve endometrial thickness in women with thin endometrium. The main questions it aims to answer are: Can exosomes delivered via subendometrial injection improve endometrial thickness or clinical pregnancy rates compared to PRP (platelet-rich plasma)? Are there significant differences in endometrial thickness between the two treatment groups? Researchers will compare the intervention groups, which one group receives mechanical exosomes and the other receives conventional esosomes via subendometrial injection, to the control group, which receives PRP via the same methods, to see if exosomes provide superior therapeutic effects. Participants will: Receive either mechanical exosomesor or conventional esosomes or PRP through subendometrial injection. Be monitored for changes in endometrial parameters.

The goal of this observational study is to determine if thin endometrial lining that is unresponsive to estrogen might be associated with the presence of senescent cells in patients following long-term use of oral contraceptives. The main question it aims to answer is: Are there any senescent cells present in thin endometrial lining? During the luteal phase of the cycle, participants will will undergo: * Gynecologic US to measure the endometrial lining thickness and pattern. * Endometrial biopsy with Pipelle catheter