Defining the proliferative phase endometrial defect

ObjectiveTo evaluate proliferative phase endometrial development in a heterogeneous infertility population.DesignRetrospective study.SettingUniversity-based infertility practice.Patient(s)Two hundred forty-six treatment cycles.Intervention(s)Clomiphene citrate or FSH ovarian stimulation, followed by IUI or IVF.Main Outcome Measure(s)Endometrial thickness according to transvaginal ultrasonography; clinical pregnancy rate.Result(s)Endometrial growth began from a nadir of approximately 4.5 mm on cycle day 4 and increased linearly to a plateau of approximately 10 mm on cycle day 9. This same pattern was observed in all cycles, regardless of pregnancy, drug, or underlying diagnosis. Follicle-stimulating hormone–stimulated cycles showed a significantly increased endometrial thickness compared with clomiphene citrate cycles (10.1 vs. 8.3 mm). Maximum endometrial thickness achieved showed a correlation with age, body mass index, and maximum E2 level. Subjects who carried a primary diagnosis of polycystic ovary syndrome, endometriosis, or recurrent pregnancy loss all achieved a significantly lower peak endometrial thickness than control subjects. There was a trend toward increased endometrial thickness in cycles resulting in pregnancy compared with those not (10.1 vs. 9.6 mm, respectively).Conclusion(s)Endometrial development follows a predictable pattern, with a plateau in growth at cycle day 9. Diseases associated with infertility manifest a proliferative phase defect that can be recognized clinically.