Preovulatory progesterone rise during ovarian stimulation for IVF.

The aim of this review is to analyze the relationship between the preovulatory progesterone (P) rise and the in vitro fertilization (IVF) pregnancy outcome. It also investigates the sources and effects of P level increase, including the underlying mechanisms and potential strategies in preventing its elevation during ovarian stimulation. The origin of production of P in the early follicular phase is adrenal which shifts toward the ovaries prior to the ovulation. Several factors contribute to the etiology of P level increase including the number of multiple follicles, the overdose of gonadotropins and poor ovarian response. Nowadays, the influence of the preovulatory P rise on IVF outcome remains controversial. Several authors have failed to demonstrate any negative impact, while others reported a detrimental effect associated with the rise of P. It seems that P rise (≤ 1.5 ng/ml or 4.77 nmol/l) may have deleterious effects on endometrial receptivity, namely, accelerating the endometrial maturation process that subsequently narrows the time-frame for implantation and thus decreases pregnancy rates. To prevent a P rise, it might be preferable to use milder stimulation protocols, earlier trigger of ovulation, cryopreservation of all embryos and transfer in the natural cycle.