In vitro maturation of oocytes: what is already known?

Assisted reproductive technologies (ARTs) involve the laboratory manipulation of gametes and embryos to help couples with fertility problems become pregnant. One of these procedures, controlled ovarian stimulation, uses pharmacological agents to induce ovarian and follicular maturation in vivo. Despite the effectiveness in achieving pregnancy and live births, some patients may have complications due to over-response to gonadotropins and develop ovarian hyperstimulation syndrome. In vitro maturation (IVM) of oocytes has emerged as a technique to reduce the risk of ovarian hyperstimulation syndrome, particularly in women with polycystic ovary syndrome, and for fertility preservation in women undergoing oncological treatment. Although there are some limitations, primarily due to oocyte quality, recent advances have improved pregnancy success rates and neonatal and infant outcomes. Different terms have been coined to describe variations of IVM, and the technique has evolved with the introduction of hormones to optimize results. In this review, we provide a comprehensive overview of IVM relating hormonal priming, culture system and media, and clinical indications for IVM with its reproductive outcomes during ARTs.