Defining the proliferative phase endometrial defect.

OBJECTIVE: To evaluate proliferative phase endometrial development in a heterogeneous infertility population.
DESIGN: Retrospective study.
SETTING: University-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 E(2) 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.