The stimulation of the development of several eggs

Normally the human ovary is designed to produce one egg a month. However, if you are undergoing in vitro fertilisation treatment and only one egg is available, the chances of pregnancy are fairly slim. It is therefore important to cause several eggs to develop simultaneously within the ovary. This is achieved by giving you daily injections of a hormone (FSH) which is the same hormone your brain naturally produces to stimulate your ovaries. Because you are receiving higher doses of this hormone than your brain would normally produce, more than one egg develops.

The number and maturity of eggs that you are producing is assessed by ultrasound examination of the ovaries. The ultrasound does not show the eggs themselves but the fluid filled structures (follicles), which contain the eggs. This is performed at intervals during your treatment. Typically, you would have approximately four ultrasound scans over the course of your treatment cycle. When the scan shows that the follicles, and therefore the eggs, are properly mature you will be scheduled to have a late evening injection (ovitrelle) to cause the final ripening of the eggs. The eggs will be collected thirty-seven hours later.