Gamete and embryo selection finalization for the improvement of clinical efficiency and efficacy represents the “holy grail” of assisted reproduction technologies (ART). Embryos are routinely assessed and selected or ranked for embryo transfer on the basis of static or dynamic morphological criteria or, less frequently, their chromosomal status. Sperm are also subject to methods of isolation from semen to pre-select a population with improved motility and morphology to maximise the chances of fertilisation. Oocyte selection, i.e. selective use based on different morphological patterns which are presumed to be prognostic of different developmental potential, is a less accepted and practiced concept in in vitro fertilisation (IVF) laboratories. Two major reasons concur to make oocyte selection controversial: i) the usually limited number of oocytes retrieved in each ovarian stimulation cycles; ii) the uncertainty of possible associations between different dysmorphisms and downstream impacts on laboratory or clinical outcomes. Oocyte dysmorphisms can affect both the intra- and extracellular morphological domains of the mature oocyte. Oocyte abnormalities can also occur with different degrees of severity and different localisations. In addition, in the absence of specific non-invasive markers, some types of dysmorphisms may be difficult to discriminate by simple morphological observation. All these factors complicate oocyte morphological selection according to appropriate standards of reproducibility and precision, preventing its adoption as a universally accepted procedure.

The number of retrieved oocytes is one of the major parameters by which the intensity of ovarian stimulation is estimated. While conventional stimulation protocols in in vitro fertilization (IVF) are designed to obtain maximum oocytes yields, they have often been associated with increased risk of complications, increased costs derived from higher gonadotropin dosage, and lower embryo quality. For these reasons, physicians have introduced a milder approach to ovarian stimulation, focusing on a more patient-friendly and safe method, while attempting to improve IVF outcomes. Typically, the strengths of mild stimulation include: reduced mean number of days of stimulation, smaller total amount of gonadotropins, smaller mean number of oocytes retrieved balanced by possibly better embryo quality, decreased treatment discomfort, and reduced risk of complications. However, to date there are still unanswered questions about the possibility that a milder approach to ovarian stimulation is clinically superior to conventional regimens.

The IVF laboratory is central to Medically Assisted Reproduction perhaps representing also the most crucial extrinsic factor in determining success or failure of treatment. Current science and technology are unable to improve the intrinsic developmental potential of gametes. Therefore, the “mission” of the IVF laboratory consists in the ability to preserve the innate characteristics of sperm and oocytes in the course of preimplantation development and minimize the possible detrimental impact of diverse forms of manipulation. To this end, during culture and manipulation, physical factors (e.g., temperature, atmosphere composition) and stressors (e.g., oocyte microinjection, embryo biopsy) should be monitored and controlled, in order to guarantee stability of conditions considered to be the most appropriate to support and facilitate gamete and embryo function in vitro. In this scenario, the human factor and effectiveness of technical equipment contribute in similar or equivalent proportions in determining clinical outcome. In light of this, not only is monitoring of working conditions of equipment important, but objective assessment of key segments of the IVF process is vital. Performance indicators respond to this need, offering specific, important, and objective measurements of essential processes, such as fertilization, development to blastocyst stage, and cryopreservation. Thus, critical analysis and interpretation of indicators can lead to consistency of results and continued improvement.