IVF means In Vitro Fertilisation ie Fertilisation in the glass. In the beginning of the ART era spem cells were added to the egg cell for fertilisation. This is still the method used and called IVF.
After collection of the eggs – these may mature for some ours in the lab – purified sperm cells are added in numbers around 100 – 200.000 to each cell.
The day after egg collection the occytes are examined for fertilisation by demonstrating presence of two pronuclei – one from the woman and one from the man.
The second day after aspiration the fertilised eggs now called embryos are examined for number of cleaved cells called blastomers and for presence of small granules in the eggs so called fragments.
Often embryos are transferred at day 2 or later at blastocyst stage.