Fertilization failure in IVF is particularly common where there are grossly abnormal semen parameters or where the number of active spermatozoa is insufficient. Gamete micromanipulation is the only way to overcome this problem and offer assistance to couples who previously had to rely on the use of donor sperm. The ICSI procedure entails the deposition of a single sperm into the main body of the egg (cytoplasm) thus bypassing the outer layers of the egg (zona pellucida). The whole procedure is performed in the lab by the embryologists using special equipment, for egg and sperm manipulation, under the control of high-powered microscopes.
ICSI is usually carried out in cases of severe male infertility (low number of active sperm or increased number of abnormal shape) and is also suggested in couples who have undergone multiple conventional IVF cycles with low fertilization rate. Finally, retrieval of low number of oocytes, the existence of sperm with no acrosome unable to penetrate the oocyte or oocytes with thick zona pellucida represent further indications for the performance of this procedure.