background: Our aim was to study ways to improve IVF success rates in women with suspected endometrial receptivity defects. methods: We conducted a retrospective cohort study examining the effect of letrozole (aromatase inhibitor) on integrin expression as a marker of endometrial receptivity. We compared IVF outcomes in 97 infertile women who had undergone anb3 integrin assessment by immunohistochemistry in mid-luteal endometrial biopsies. Of 79 women undergoing standard IVF, 29 (36.7%) lacked normal integrin expression. Eighteen other women with low integrin were studied after receiving letrozole during early IVF stimulation. An independent set of anb3 integrin-negative patients (n ¼ 15) who had undergone repeat endometrial biopsy for integrin testing while taking letrozole were re-evaluated.results: Clinical pregnancy and delivery rates were higher in women with normal anb3 integrin expression compared with those who were integrin negative [20/50 (40%) versus 4/29 (13.8%); P ¼ 0.02 and 19/50 (38%) versus 2/29 (7%); P , 0.01, respectively]. In 18 women who received letrozole early in IVF, 11 conceived (61.1%; P , 0.001) compared with integrin-negative patients who did not receive letrozole. In integrin-negative women who were rebiopsied on letrozole, 66.7% reverted to normal integrin expression. Positive endometrial aromatase immunostaining using a polyclonal antibody was a common finding in infertile patients compared with controls.conclusions: Lack of endometrial anb3 integrin expression is associated with a poor prognosis for IVF that might be improved with letrozole co-treatment. Prospective studies are needed to confirm and extend these findings but the data suggest that aromatase expression may contribute to implantation failure in some women.

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