In the process of treating infertility with Intracytoplasmic Sperm Injection (ICSI), multiple eggs in the ovaries are simultaneously stimulated and retrieved. After retrieval, each egg is denuded of the cumulus cells for evaluation of the maturation profile. The retrieved eggs exist in one of these stages: germinal vesicle (GV) oocytes, metaphase I (MI) or immature oocytes, and metaphase II (MII) or mature oocytes. However, only the oocytes at MII stage will be used for ICSI.
Immature oocytes will be incubated overnight for in vitro maturation, and those that are not fertilized will be discarded. Some immature oocytes can undergo maturation to MII stage and can be subjected to ICSI, more specifically known as ICSI Late Mature oocyte (ICSI/LM). The procedure of ICSI/LM is identical to that of ICSI, with the only difference being that the oocytes used for ICSI/LM are late-maturing oocytes retrieved from the same cycle. Accordingly, ICSI/LM allows for more utilization of the immature oocytes that have the potential to be used for ICSI.
Although ICSI/LM may have a lower embryo cleavage rate than ICSI cycles, it cannot be denied that ICSI/LM helps increase the number of embryos that suitable for transfers, which is especially useful for patients with absence of mature oocytes after ICSI cycles and also patients with a low number of mature oocytes or lack of good quality embryos for transfer.
Therefore, ICSI late mature oocyte is considered an alternative to the regular ICSI, aimed at increasing the number of embryos, the chances for embryo transfer, and ultimately the success rate of fertility treatment.
Medical Technician, Embryo Laboratory