Do you want to What is The ICSI Treatment ?. Intra Cytoplasmic Sperm Injection (ICSI) Naturally, the fertilisation process involves the penetration of a single sperm from the ejaculate into the egg (called oocyte in scientific terms) released during the menstrual cycle. Said sperm must penetrate the shell of the oocyte (called zona pellucida) to immediately fuse with the female gamete. Sometimes, either due to physiological deficiencies that may lead to a drastic reduction or absence in the production of gametes or due to poor gamete quality or defects in the interaction, the process of fertilisation can be diminished or even prevented. From the Assisted Reproduction Techniques (ART) perspective there are two main approaches to overcome these deficiencies: 1. Conventional In Vitro fertilisation (IVF) 2. Intra Cytoplasmic Sperm Injection (ICSI).