| Intracytoplasmic sperm injection | |
|---|---|
 Oocyte cytoplasm is injected with the sperm during ICSI | |
| MeSH | D020554 |
Intracytoplasmic sperm injection (ICSI /ˈɪksi/ IK-see) is an in vitro fertilization (IVF) procedure in which a single sperm cell is injected directly into the cytoplasm of an egg. This technique is used in order to prepare the gametes for the obtention of embryos that may be transferred to a maternal uterus. With this method, the acrosome reaction is skipped.
There are several differences between classic IVF and ICSI. However, the steps to be followed before and after insemination are the same. In terms of insemination, ICSI needs only one sperm cell per oocyte, while IVF needs 50,000–100,000. This is because the acrosome reaction has to take place and thousands of sperm cells have to be involved in IVF. Once fertilized, the egg is transformed into a pre-embryo and it has to be transferred to the uterus to continue its development.
The first human pregnancy generated by ICSI was carried out in 1991 by Gianpiero Palermo and his team.