In premature luteinization, progesterone induces secretory transformation of the endometrium without impairment of embryo viability

Objective: To determine the effect of serum P on endometrial histology in stimulated cycles. Design: Prospective clinical study. Setting: Community hospital-based donor oocyte program. Patient(s): Fertile young oocyte donors and infertile donor oocyte recipients. Intervention(s): Oocyte donors underwent gonadotropin stimulation after midluteal pituitary suppression. Endometrial biopsies were obtained at the time of oocyte retrieval. Main Outcome Measure(s): Endometrial histology and serum P levels in oocyte donors. Pregnancy and implantation rates in oocyte recipients. Result(s): Thirteen biopsy specimens (52.0%) showed in-phase mixed proliferative pattern (days 14 to 15), whereas 12 (48.0%) were secretory (days 16 to 17). On the day of hCG, subjects with secretory endometrium had higher P of 1.7 ng/mL (5.4 nmol/L) than women with the mixed pattern (0.8 ng/mL [2.5 nmol/L]). Progesterone greater than or equal to 0.9 ng/mL had a 78.6% positive predictive value for secretory transformation. In 75.0% of cycles with secretory endometrium, P was greater than or equal to 0.9 ng/mL (2.9 nmol/L) as early as 2 days before hCG. Both mixed and secretory patterns were associated with similar clinical pregnancy rates (57.1% and 60.0%, respectively) and delivery rates (38.1% and 50.0%, respectively) in recipients. Conclusion(s): Subtle elevation of P induced secretory endometrial transformation without reduction in embryo viability. (C) 1997 by American Society for Reproductive Medicine.