P-355 Thin endometrium is associated to higher risk of having a displaced window of implantation (WOI)

Abstract Study question Is thin endometrium (<6 mm) associated to an abnormal receptivity status? Summary answer Thin is significantly with a displaced WOI. What known already The measurement of endometrial thickness by 2D vaginal ultrasound (US) routine practice in Assisted Reproduction Techniques (ART). poor reproductive outcome; however, the potential reason unknown. design, size, duration Retrospective cohorts study including 25,888 patients which lining was measured US day before progesterone supplementation HRT cycles for frozen embryo transfers and Endometrial Receptivity Analysis (ERA) performed after 5 days administration. classified as < 6 mm, 6-12 or > 12 mm; ERA results were considered receptive WOI (Pre-receptive, post-receptive, proliferative, late-receptive) that needs personalized transfer (pET). Participants/materials, setting, methods from one layer other on longitudinal transvaginal scan at site maximum evidenced US. For analysis, RNA extracted sequenced NGS. Then, computational predictor obtained diagnosis standard Main role chance RA reveal women (<6mm) present higher incidence (47.49%) than 6-12mm (38.20%) (p = 0.0038), >12mm (39.75%) 0.026). No differences found. *Significant different against two groups. Global Chi-square test association P 0.002. Limitations, reasons caution This retrospective study, having innate limitations its nature. Wider implications findings compared normal hypertrophic endometrium. Normal (6-12 “receptive” does not preclude transcriptomic status 38.20% cases. finding should be when planned. Trial registration number Not applicable