PREGNANCY AND IMPLANTATION RATES IN NORMAL REPLACEMENT VERSUS STIMULATED CYCLES

The relative importance that endometrial development and embryo qualit y have on implantation rates achieved with assisted reproductive techn ology (ART) is the subject of controversy. Ovarian stimulation has bee n repeatedly mentioned as having a detrimental effect on endometrial r eceptivity (Paulson et al., 1990, Fertil. Steril., 53, 870 - 874). We compared pregnancy and implantation rates achieved with ART during sti mulated cycles and hormonal replacement cycles, in patients matched fo r the following criteria: age < 35 years for the patient donating oocy tes; transfer of at least two good quality embryos/oocytes and good qu ality transfer. All transfer cases performed during hormonal replaceme nt cycles were done with donated oocytes. Comparison of results betwee n techniques was not attempted due to potential differences in populat ions. The pregnancy and implantation rates achieved with each techniqu e during stimulated and hormonal replacement cycles were not statistic ally different. In contradiction to previous results, our data suggest that differences in uterine receptivity between stimulated and hormon al replacement cycles in the age group studied are not of critical imp ortance in embryo implantation. Good embryo quality appears to be the dominant factor in determining the success of ART.