ICSI refers to Intracytoplasmic Sperm Injection, an IVF technique that involves direct injection of a selected sperm into an egg.
In some circumstances where standard IVF treatments require manual introduction between the egg and the sperm, this intimate procedure allows the sperm the highest possible chance of fertilising the egg. Just as other In Vitro Fertilisation procedures, these processes are accomplished outside the womb, with the viable embryo being returned to the womb for gestation. The risk of multiple births does not increase through the use of ICSI and, along with Assisted Hatching, is a procedure that offers a high probability of success.
ICSI has such a great impact in the field that now it has become a routine procedure in most fertility clinic laboratories.
Who should use ICSI?
Initially used exclusively for severe male factor infertility, ICSI has now acquired additional indications. Poor oocyte quality, thickened zona pellucidae, advanced age, limited number of oocytes due to poor response and moderate male factor infertility are some of these new indications for ICSI.
According to statistics, 50-80% of eggs are successfully fertilised through ICSI. Once this takes place, the now-fertilised egg begins to divide on a cellular level, and the viable embryos are then reintroduced to the woman’s uterus.
How does it work?
For normal conception, millions of sperm race through a woman’s vagina, pass the cervix, through the uterus and then fallopian tubes to fertilise a single egg (or more in the case of fraternal twins, triplets, etc.). Out of all those that start the race, only one will complete the journey.
Each sperm is characterised by its oval head and long tail, which it uses to propel its way through a woman’s reproductive system toward the fallopian tubes. The winning sperm’s head attaches to the outer layer of an unfertilised egg and pushes through to the inner cytoplasm, thus completing the fertilisation process. The egg reacts to this by hardening its outer cell wall, negating attempts by other sperm to follow suit.
Sometimes, males produce too few sperm, ill-formed sperm, or sperm that cannot attach themselves to the egg properly. In these cases, ICSI can be a highly successful method for conception.
As a part of our IVF treatments, our embryologists can insert a tiny needle through the cell wall of an unfertilised egg and deliver a single sperm cell to fertilise it. This is done on a microscopic scale with a micro-pipette and micro-injector being utilised to manipulate the cell and introduce the single sperm into the egg. The sperm’s tail is removed for greater control during the injection process.
Very recently, cryopreserved oocytes have been fertilised by ICSI and the resultant embryos have given rise to live birth IVF success rates. This procedure will undoubtedly be applied in more settings in the future and may even become the method of choice for fertilising all oocytes so that there are no unexpected fertilisation failures and to avoid polyspermic fertilisation.