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Sunday, 22 June 2014

ICSI: Intracytoplasmic sperm injection

Conventional IVF involves placement of motile sperms in close proximity of the eggs (oocytes). The sperms release enzymes that disperse the cumulus cells around the eggs and one of the sperms then penetrates the shell of the egg and the combination of egg and sperm leads to the formation of an embryo. When the motility of sperms is less or the number is insufficient, fertilisation may fail to occur. Intracytoplasmic Sperm Injection is the technique used to overcome this situation. ICSI is also required in cycles where PGD or PGS is employed as otherwise erroneous results may occur. 

The procedure is carried out in the embryology laboratory. Oocytes are normally surrounded by a thick fluffy cluster of cells (cumulus cells). In order to perform ICSI, the oocytes need to be denuded which means the cumulus cells need to be removed from around the oocytes by chemical or mechanical means. Denudation is essential for smooth and correct ICSI technique. Only mature eggs can be used for ICSI. The immature eggs cannot be used as these will form abnormal embryos.

The pregnancy rates and outcomes of cycles do not vary with the technique used for fertilisation (i.e., IVF versus ICSI). Embryo created are not superior to those produced after IVF and hence the decision to perform ICSI is based on the assessment of the couple and the embryologist's assessment of the semen parameters on the day of the egg collection. 

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