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 E(2) concentrations in serum, and negatively associated with advanced age. Endometrial thickness was dependent on peak E(2) 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 dependent on patient age, duration of ovarian stimulation, and embryo quality.