Artificial endometrial preparation for oocyte donation: the effect of estrogen stimulation on clinical outcome

Morphologic studies of the endometrium have demonstrated that varying the duration of an artificial follicular phase (AFP) in women with ovarian failure did not adversely affect its developmental capacity. The aim of this study was to evaluate whether such manipulations of endometrial stimulation could influence the pregnancy rate in women undergoing oocyte donation (OD). Twenty-nine women were investigated in 51 cycles of OD. Endometrial preparation was performed with a fixed dose of micronized estradiol, 4 mg/day, administered for 5-35 days in accordance with oocyte availability. On the day of donation progesterone in oil, 50 mg/day, was added to the regimen. Oocytes were donated anonymously by patients undergoing routine in vitro fertilization. Fifteen clinical pregnancies were achieved, for a success rate of 29.4%. Using logistic regression analysis the success rate was found to be closely associated with the duration of estrogen stimulation. The pregnancy rate was 7.7, 52, and 7.7% after an AFP of 4-11, 12-19, and 20-29 days, respectively. It seems that for optimal results in an OD program, estrogen stimulation should be kept at between 12 and 19 days. These results also imply that, contrary to endometrial morphology, which seems to be tolerant to extreme AFP durations, functional receptivity is less permissive and is adversely affected by such manipulations.