In vitro fertilisation and embryo transfer (IVF-ET)
Following the assessment of their maturity, based on the morphology of the cellular layers surrounding them, the ova are placed inside the appropriate nutrients and incubated for 2-4 hours before the sperm is introduced. Approximately 18 hours after the spermatozoa have been introduced, the ova are checked for the presence of 2 pro-nuclei (male and female); this confirms that fertilisation has been achieved. When the sperm is normal, the rate of ova fertilisation is around 60%-70%.
Incubation continues for another 24 to 48 hours, when the division of the fertilised ova is checked, at which point they are usually at the stage of 4 to 8 cells, respectively. At this stage, i.e. 48-72 hours later, the fertilised ova are usually transferred into the uterus. This procedure does not require anaesthesia and is performed with the aid of special catheters. In recent years the extension of fertilised ova cultivation to a total of 5-6 days is being tested; this means that the ova continue to divide and reach the blastocyst stage. This way, the best embryos are selected for embryo transfer, namely those that have reached the blastocyst stage. After the embryo transfer, medication is usually administered, such as natural progesterone, for the best possible preparation of the endometrium and so as to strengthen the implant.