ERA in Young Primary Infertile RIF Patients

Young women with recurrent implantation failure (RIF) will be prospectively recruited and classified based on their Window of Implantation (WOI) status. Clinical outcomes will be compared between patients undergoing personalized embryo transfer (pET) and those receiving standard transfer. Concurrently, endometrial tissues collected at P+3 and P+5 will undergo RNA sequencing to elucidate the molecular mechanisms underlying abnormal receptivity. Integrating these clinical and transcriptomic data, we aim to develop a clinical prediction model for displaced WOI and validate the efficacy of pET in improving pregnancy outcomes for this specific population.

• RIF Cohort - Inclusion Criteria

• Age ≤ 35 years; BMI 18-25 kg/m².
• ≥ 3 failed transfers of high-quality embryos.
• No history of spontaneous or FET-related pregnancy, including biochemical pregnancy (primary infertility).
• Written informed consent provided.
• RIF Cohort - Exclusion Criteria

• Known factors associated with RIF, including: uterine anatomical abnormalities (malformations, adhesions, polyps, submucosal fibroids, adenomyosis) and hydrosalpinx
• Endocrine disorders (PCOS, thyroid dysfunction, hyperprolactinemia)
• Reproductive immunological abnormalities, thrombophilia and infectious factors, abnormal semen parameters,
• Chromosomal abnormalities in either partner (planned PGT-SR) or monogenic disease (planned PGT-M).
• Severe medical/surgical conditions contraindicating pregnancy.
• Any other condition deemed unsuitable by the investigators.
• Control Group - Inclusion Criteria

• Age ≤ 35 years; BMI 18-25 kg/m².
• First IVF-ET cycle due to tubal factor infertility.
• No history of biochemical pregnancy or miscarriage.
• Written informed consent provided.
• Control Group - Exclusion Criteria 1. Same as RIF Cohort Exclusion Criteria. Additionally, participants with an abnormal ERA result will be excluded from the control group.