Microinjection (ICSI)

Fertilization whether spontaneous or in vitro does occur between one egg (oocyte) and one sperm. All other sperms produced at ejaculation has a very important task to fulfil, though. These fellow sperms will assist the essential sperm in its aim to fertilize the oocyte.

At ovulation the oocyte is surrounded by mucus called cumulus. This cumulus has to be disintigrated by enzymes brought there by the sperms. To be able to dissolve this cumulus a large number of sperms are necessary. If this does not happen, the sperm will not be able to fertilize. Even after the cumulus is dissolved and the sperm reaches the shell of the oocyte (the zona), this surrounding zona has to be subjected to enzymes from the sperms. This procedure does also call for a large number of sperms.

If the number of sperms is low, or the quality is decreased, this collaboration between the sperms can not take place and the cumulus and the zona will not be penetratable. There are a lot of conditions that can give rise to a low sperm count or a decreased quality in the sperm and its ability to fertilize.

Mumps is an infection that, when affecting the male around the time of puberty, can give rise to a low sperm count. There are also other infections later in life that might have a similar effect on the sperm quality.

If this is the situation, the sperm could be injected directly through the zona into the oocyte to enable fertilization. In case this procedure is necessary based on the previous investigations the hormonal treatment and the monitoring is initiated in the same way as in the standard IVF procedure. The different actions to be taken will not take place until the oocytes and the sperms are taken care of in the laboratory.

When the male has produced his sperm sample on the day of the oocyte recovery, the sperms are prepared in a specific way. Often, the number of sperms are much less than in the ordinary IVF procedure. In the standard IVF procedure roughly 20.000 sperms are put together with each oocyte. In the situations where microinjection is needed anything from 10 to 100 sperms might be the maximum retrieved. In this situation the oocyte is enzymatically prepared to remove the cumulus. When the cumulus is removed the oocyte is immobilized by a holding-pipette to enable an even thinner hollow glass needle containing one single sperm to be introduced through the zona into the oocyte. The whole procedure is done under microscopic supervision. After all oocytes have been microinjected with one sperm each, they are returned to the incubator and the procedure goes on as in the standard IVF procedure.