Intracytoplasmic sperm injection (ICSI) is a laboratory technique used during IVF. Instead of letting fertilization happen naturally in a dish, an embryologist injects a single sperm directly into each mature egg.
The rest of the treatment is the same as IVF: stimulation, egg collection, embryo development and transfer. ICSI can help overcome some barriers to fertilization, but it does not guarantee that eggs will fertilize or develop.