Reproductive biology and IVF: ovarian stimulation and luteal phase consequences

Most clinicians working in in vitro fertilization (IVF) centers worldwide have taken for granted for more than a decade the paradigm of so-called 'controlled' ovarian hyperstimulation, using maximum stimulation by exogenous gonadotropins, together with the gonadotropin-releasing hormone (GnRH) agonist long-protocol. Potential detrimental effects of this approach with regard to oocyte quality, corpus luteum function and endometrial receptivity have been largely ignored. These factors might by themselves have a major impact on IVF outcome and should therefore be considered seriously. The recent introduction of GnRH antagonists along with the current emphasis on the need for transfer of a reduced number of embryos enables a careful re-evaluation of current IVF strategies. We can now render stimulation protocols simpler, starting with a spontaneous menstrual cycle, allowing for more subtle interference with single dominant follicle selection. Here, we discuss recent approaches to ovarian stimulation, the induction of oocyte maturation, and effects of these altered follicular phase interventions on corpus luteum function following ovarian stimulation.