However, there is scarce data comparing the use of GnRH antagonists from day 1 of IVF stimulation versus standard flexible antagonist administration from day 5/6 in PCOS patients undergoing IVF cycles, in terms of possible impact on quantitative and qualitative laboratory and clinical outcome parameters such as number of oocytes retrieved, fertilization rate resulting in optimal 2PN embryos, number of embryos formed, proportion of top-quality embryos achieved, and pregnancy rates. The gene discussed is GNRH1; the disease is polycystic ovary syndrome.