ICSI

ICSI is generally performed following an in vitro fertilization procedure to extract one to several oocytes from a woman.

 

The procedure is done under a microscope using multiple micromanipulation devices (micromanipulator, microinjectors and micropipettes). A holding pipette stabilizes the mature oocyte with gentle suction applied by a microinjector. From the opposite side a thin, hollow glass micropipette is used to collect a single sperm, having immobilised it by cutting its tail with the point of the micropipette. The oocyte is pierced through the oolemma and directed to the inner part of the oocyte (cytoplasm). The sperm is then released into the oocyte. The pictured oocyte has an extruded polar body at about 12 o'clock indicating its maturity. The polar body is positioned at the 12 or 6 o'clock position, to ensure that the inserted micropipette does not disrupt the spindle inside the egg. After the procedure, the oocyte will be placed into cell culture and checked on the following day for signs of fertilization.

 

In contrast, in natural fertilization sperm compete and when the first sperm penetrates the oolemma, the oolemma hardens to block the entry of any other sperm. Concern has been raised that in ICSI this sperm selection process is bypassed and the sperm is selected by the embryologist without any specific testing. However, in mid-2006 the FDA cleared a device that allows embryologists to select mature sperm for ICSI based on sperm binding to hyaluronan, the main constituent of the gel layer (cumulus oophorus) surrounding the oocyte. The device provides microscopic droplets of hyaluronan hydrogel attached to the culture dish. The embryologist places the prepared sperm on the microdot, selects and captures sperm that bind to the dot. Basic research on the maturation of sperm shows that hyaluronan-binding sperm are more mature and show fewer DNA strand breaks and significantly lower levels of aneuploidy than the sperm population from which they were selected. A brand name for one such sperm selection device is PICSI. A recent clinical trial showed a sharp reduction in miscarriage with embryos derived from PICSI sperm selection.

 

'Washed' or 'unwashed' sperm may be used in the process.

 

Live birth rate are significantly higher with progesterone for luteal support in ICSI cycles. Also, addition of a GNRH agonist for luteal support in ICSI cycles has been estimated to increase success rates, by a live birth rate RD of +16% (95% confidence interval +10 to +22%).

 

Using ultra-high magnification during sperm selection (with the technique being called IMSI) has no evidence of increased live birth or miscarriage rates compared to standard ICSI.

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