Ovarian stimulation for IVF profoundly alters the early luteal phase endometrial development. It has been hypothesized that this process has already started in the late follicular phase, as the endometrium has already been exposed to high steroid concentrations since that phase. The aim of the present study was to prospectively investigate the effect of multi-follicular ovarian stimulation for IVF on the late follicular phase endometrium histology and the expression of estrogen receptor (ER) and progesterone receptor (PR).
Steroid receptor expression in late follicular phase endometrium in GnRH antagonist IVF cycles is already altered, indicating initiation of early luteal phase transformation in the absence of secretory changes.
