Accelerated endometrial maturation in the luteal phase of cycles utilizing controlled ovarian hyperstimulation: impact of gonadotropin-releasing hormone agonists versus antagonists.

OBJECTIVE: To evaluate the endometrium obtained during the luteal phase of controlled ovarian hyperstimulation (COH) cycles utilizing gonadotropin-releasing hormone (GnRH) antagonists, and to compare these findings with those obtained in cycles utilizing a GnRH agonist and with artificial cycles among recipients.
DESIGN: Prospective evaluation of oocyte donors.
SETTING: University-based in vitro fertilization (IVF) center. PATIENT(S): Fifteen oocyte donors undergoing standard COH were enrolled in 1 of 3 COH groups, and 40 recipients of oocyte donation were used as a control group. INTERVENTION(S): Controlled ovarian hyperstimulation and endometrial biopsy. MAIN OUTCOME MEASURE(S): Histological dating of endometrial biopsies, serum estradiol (E(2)) and progesterone levels. RESULT(S): On the day of oocyte retrieval, endometrial maturation was advanced by an average of 5.8 +/- 0.4 days in the antagonist group and 5.9 +/- 0.7 days in the agonist group. This advancement persisted on day 7 postoocyte retrieval. Serum progesterone levels were elevated before human chorionic gonadotropin (hCG) administration, but remained similar in both groups. CONCLUSION(S): Controlled ovarian hyperstimulation is associated with elevated progesterone levels in the late follicular phase and accelerated endometrial maturation in the subsequent luteal phase. No significant differences exist between preretrieval serial serum progesterone levels and luteal phase endometrial histology between cycles utilizing GnRH agonists or antagonists.