SELL and Infertility: Elsewhere, Ganesh et al., in a preliminary study reported that OS with the use of letrozole was associated with a significant increase in the epithelial and stromal expression of uterine receptivity markers, including integrin, leukaemia inhibitory factor, and L-selectin, in women with unexplained infertility compared with natural cycles [23]; all of which may have positive effects on the pregnancy rate after ET [2].