Evaluation of cycle-to-cycle variation of endometrial responsiveness using transvaginal sonography in women undergoing assisted reproduction

Objectives <p>To investigate the variation of endometrial responsiveness between cycles within the same women undergoing assisted reproduction. <p>Methods <p>The sonographic endometrial thickness in ovarian stimulation cycles was compared with that of subsequent natural cycles. One hundred and thirty-six ovarian stimulation cycles of <i>in-vitro</i> fertilization and embryo transfer were evaluated. Women who did not conceive in <i>in-vitro</i> fertilization cycles were subsequently seen in natural cycles (<i>n</i> = 97) or the next <i>in-vitro</i> fertilization cycle (<i>n</i> = 39). Based on a receiver-operating characteristics (ROC) curve using endometrial thickness to predict pregnancy, the first <i>in-vitro</i> fertilization cycles were classified according to the endometrial thickness as optimal (<i>></i> 8 mm) in 98 cycles, or suboptimal (<i>≤</i> 8 mm) in 29 cycles. Similarly, spontaneous cycles were classified as suboptimal (<i>≤</i> 7 mm) in 28 cycles and optimal (<i>></i> 7 mm) in 69 cycles. <p>Results <p>The pregnancy rates were significantly lower (<i>P <</i> 0.05; Fisher's Exact test) in the suboptimal group in both the <i>in-vitro</i> fertilization and frozen embryo transfer cycles. There was a strong correlation (<i>r</i> ² = 0.745) and a significant difference (<i>P</i> < 0.001; Wilcoxon signed rank sum test) between the endometrial thickness of stimulation and natural cycles. <p>Conclusion <p>It is possible to predict the occurrence of optimal or suboptimal endometrial response in natural cycles of women, after evaluation in stimulated cycles, with a high degree of reliability. Risk of implantation failure can be identified before subsequent treatment cycles and adjuvant therapeutic strategies may be planned to improve the endometrial response before embryo transfer.