Influences on endometrial development during intrauterine insemination: clinical experience of 2,929 patients with unexplained infertility.

ObjectiveTo characterize relationships associated with adverse endometrial development in patients undergoing IUI for unexplained infertility.DesignA retrospective review of 2,929 patients from 2004-2011.SettingLarge metropolitan infertility practice.Patient(s)Patients with unexplained infertility undergoing first IUI cycle at age less than 43 years, with a total motile sperm count ≥ 8 million.Intervention(s)Clomiphene citrate (CC) with FSH stimulation followed by IUI.Main outcome measure(s)Endometrial thickness, serum E2 (in picograms per milliliter) levels on the day of hCG trigger administration, body mass index (BMI) (in kilograms per meter squared), total motile sperm, follicle number, and clinical pregnancy.Result(s)Of the 2,929 patients who met the inclusion criteria, 466 (15.9 %) achieved a clinical pregnancy. Pregnancy rates (PRs) increased significantly with increasing endometrial thickness on the day of hCG administration and with increasing serum E2 level, but were not significantly related to age, BMI, or follicle numbers according to multiple logistic regression modeling. Peak endometrial thickness declined with age and increasing E2 levels. The BMI was associated with thicker endometrium, but it was also associated with lower peak E2 levels.Conclusion(s)The impact of "endometrial factor" infertility may be underappreciated in IUI therapy. Targeted therapies to optimize the endometrium represent an important new area to improve in current fertility success rates.