Endometrial pinopodes and uterine receptivity.

The human endometrium is an extremely sensitive target for steroid hormones. During the menstrual cycle, this tissue undergoes dynamic changes which are reflected on the surface morphology of the epithelium, and which can be followed by scanning electron microscopy. The morphological changes peak at the midsecretory phase, with the formation of the so-called pinopodes. Increasing evidence suggests that these pinopodes are accurate markers for endometrial receptivity, and their detection may be of high clinical utility for the preparation of endometrium before embryo transfer.