Comparison of transdermal versus oral estradiol on endometrial receptivity

Objective: To compare the effects of oral micronized E(2) with transdermal E(2) on endometrial receptivity in women undergoing oocyte donation. Design: Prospective, randomized, crossover trial. Serum E(2) and P concentrations were measured on cycle days 14 and 22 (luteal day +8). Endometrial biopsies were obtained on day 22 and read in a blinded fashion for histology and beta-3-integrin expression. Setting: University-based donor oocyte program. Patients: Twenty-seven patients presenting for donor oocytes. Main Outcome Measures: Endometrial histology and P-S-integrin expression. Results: The endometrial glandular histology in women given oral micronized E(2) was delayed by a mean of 1.6 days in comparison to that of women given transdermal E(2) Seventy percent of women given oral E(2) displayed a lag greater than or equal to 4 days whereas 29.6% given transdermal E(2) displayed a similar lag. Serum E(2) levels were 1,194 +/- 108.8 pg/mL (mean +/- SEM; conversion factor to SI unit, 3.671) in women on oral micronized E(2) and 117.4 +/- 14.0 pg/mL in those on transdermal E(2). Conclusion: The supraphysiologic serum E(2) levels associated with oral micronized E(2) may have a deleterious impact on endometrial receptivity. The development of more physiologic hormone replacement protocols may enhance endometrial receptivity and lead to improved clinical pregnancy rates.