Successful implantation requires synchrony between a competent blastocyst and a receptive secretory phase endometrium. As oestrogen rises during the follicular phase and a dominant follicle emerges, OVARIES produce P, which induces endometrial secretory transformation and promotes receptivity. Fertility treatments may interfere with this production via several mechanisms. Ovulation induction (OI) may result in a premature rise of P and alterations in endometrial receptivity. Furthermore, supraphysiologic E2 elevation from ovarian stimulation may cause alterations in luteal phase (the phase after egg collection) LH secretion.
Supraphysiologic E2 levels are often associated with multifollicular development during assisted reproductive technology (ART). The use of GnRH antagonists – Cetrotide/ Orgalutran – for pituitary down-regulation and mechanical disruption of follicles during oocyte aspiration may further affect luteal function. To reverse this negative effect, we give progesterone support. Support after egg collection with exogenous P after ART is routine because it is associated with higher pregnancy and live birth rates.