New Twists in Ovarian Stimulation and Their Practical Implications

Abstract

Ovarian stimulation (OS) has for objective to induce multiple ovulation in order to yield a multiple oocyte harvest and offer multiple embryos available for transfer thereby increasing the efficacy of ART. Originally, the primary risk associated with OS was the occurrence of frank ovarian hyperstimulation syndrome (OHSS), a possibly dreadful-sometime fatal-complication of ART. These fears limited the number of oocytes aimed for during OS in order to curb the risk of OHSS. On the contrary, the meager implantation rates of the early days of ART led to easily transfer multiple embryos in order to achieve acceptable pregnancy rates. Today the perspectives have changed. The advent of antagonist-based OS protocol and the possibility to trigger the ultimate phase of oocyte maturation with GnRH-a has allowed to reduce the risk of OHHS. Conversely, the markedly increased implantation rates of today's ART makes multiple pregnancy a worry that has come in the limelight worldwide, pushing the practice of single embryo transfer (SET).

Keywords: GnRH antagonist; dual ovarian stimulation; gonadotropin; ovarian hyperstimulation syndrome (OHSS); ovarian stimulation.

Figure 1

Paralell decline in oocyte quality and quantity—primordial follicle count—as a function of age (adapted from Faddy et al. with permission).

Figure 2

Dual or duplex ovarian stimulation during the follicular and ensuing luteal phase allow to double the number of blastocyst harvested.

Figure 3

Under the influence of hCG, the hyperstimulated ovary produces the vasoactive VEGF that modifies vascular permeability leading to an efflux of vascular fluid—forming oedema and ascitis—and also leading to hemoconcentration thereby increasing the risk of venothrombo embolism (VTE).