Editing In vitro fertilisation (section)

===Egg and sperm preparation===
In the laboratory, for ICSI treatments, the identified eggs are stripped of surrounding cells (also known as [[cumulus cell]]s) and prepared for [[fertilisation]]. An [[oocyte selection]] may be performed prior to fertilisation to select eggs that can be fertilised, as it is required they are in metaphase II. There are cases in which if oocytes are in the metaphase I stage, they can be kept being cultured so as to undergo a posterior sperm injection. In the meantime, [[semen]] is prepared for fertilisation by removing inactive cells and seminal fluid in a process called [[sperm washing]]. If semen is being provided by a [[sperm donor]], it will usually have been prepared for treatment before being frozen and quarantined, and it will be thawed ready for use.{{citation needed|date=July 2020}}