Increased endometrial thickness is associated with improved treatment outcome for selected patients undergoing in vitro fertilization-embryo transfer

Objective: To examine possible relationships between endometrial thickness and treatment outcome after IVF and embryo transfer, and to explore the role of potential confounding factors that may influence such relationships. Design: Retrospective study. Setting: A university-affiliated clinical IVF center. Patient(s): Patients undergoing IVF-embryo transfer with their own oocytes. Intervention(s): None. Main Outcome Measure(s): Endometrial thickness was determined on the day of hCG administration, 2 days before oocyte retrieval. Clinical pregnancy was confirmed by ultrasound observation of fetal heart activity. Result(s): The study analyzed 897 IVF-embryo transfer cycles. Treatment outcome (clinical pregnancy) after IVF-embryo transfer was positively associated with increased endometrial thickness and peak E₂ concentrations in serum, and negatively associated with advanced age. Endometrial thickness was dependent on peak E₂ concentrations in serum, but was independent of patient age or duration of ovarian stimulation. Thin endometrium reduced PRs in relatively young patients (<38 years old), in patients who required more than 10 days of gonadotropin stimulation, or in patients whose embryo transfers consisted of poor quality embryos. Conclusion(s): Increased endometrial thickness was associated with improved treatment outcome, but this association was dependant on patient age, duration of ovarian stimulation, and embryo quality.