Treatment · 4 min read
ICSI — intracytoplasmic sperm injection — is a specialised form of IVF where a single sperm is injected directly into an egg in the laboratory. It's most often used when there's a male factor involved, or when previous attempts at fertilisation haven't worked.
First introduced in 1992, ICSI is now one of the most widely used fertility laboratory techniques in the world. According to the HFEA, a significant proportion of UK IVF cycles use ICSI, particularly where male factor infertility is a concern.
In standard IVF, eggs and sperm are placed together in a dish and fertilisation happens naturally. In ICSI, an embryologist selects one healthy-looking sperm and uses a very fine glass needle to inject it directly into the centre of the egg. Everything else about the cycle — the medication, egg collection, embryo development and transfer — is the same.
ICSI is most often suggested when sperm numbers, movement or shape are below the thresholds described by the WHO laboratory manual, when sperm have been retrieved surgically, when previous IVF cycles have had unexpectedly low fertilisation, or when frozen sperm of limited quantity is being used.
For couples with male factor infertility, ICSI clearly improves fertilisation rates compared with standard IVF. For other reasons — for example, unexplained infertility with normal sperm — large studies have not shown that ICSI gives better live birth rates than conventional IVF. A good clinic will only recommend ICSI when there's a clear reason to.
From your point of view, an ICSI cycle feels almost identical to an IVF cycle. The difference happens in the embryology laboratory and is performed by an experienced embryologist. If you'd like more context, our guide to what a clinical embryologist does walks through the laboratory side of treatment in plain English.
