In conventional IVF, eggs and many sperm are placed together in a dish and fertilization happens on its own. In ICSI, an embryologist selects one sperm and injects it directly into the egg using a fine glass needle under a high-power microscope. Everything else about the IVF cycle — stimulation, egg retrieval, embryo culture, transfer — stays the same.
When it's used
ICSI is the standard approach when sperm count, movement, or shape is significantly reduced, when sperm has been surgically retrieved from the testes, or when a previous IVF cycle showed poor or failed fertilization. For couples without male-factor issues, routine ICSI doesn't necessarily improve outcomes — it's a targeted tool, not an automatic upgrade.