What is visible on the day after the fertilisation?
Seventeen to twenty hours after the insemination the oocytes are observed under inverted microscope at 400x magnification in order to detect if fertilisation has taken place or not. A fertilised oocyte shows two pronuclei, each one of them corresponding to the female and male genetic codes.
We can find successfully fertilised oocytes, unfertilised oocytes and abnormally fertilised oocytes.
Ovocitos en dos pronúcleos
Is it possible to distinguish abnormalities in the fertilisation?
It is possible to detect abnormal fertilisations at this stage. For instance, if two spermatozoa have entered and there is a triple genetic code.
It is important to detect abnormal fertilisations, since these oocytes could divide correctly and give place to morphologically normal but genetically abnormal embryos that, under no circumstance, should be transferred.
Are all In Vitro inseminated oocytes fertilised?
No. Under normal conditions, with sperm coming from ejaculate, the fertilisation rate in IVF and in IVF- ICSI is around 70%.
The first IVF cycle of a couple is diagnostic and allows observing the fertility rate of each couple. We can observe low fertilisation rates (5-20%) or even a total failure of fertilisation.
Are embryo chromosome abnormalities more frequent in IVF than in natural reproduction?
No. Although the average age of patients who undergo IVF treatment to have their first child is higher than among the general population and, therefore, the risk of embryo abnormalities is higher, effectively no higher genetic abnormality rates are observed in babies born by IVF.
In addition, the IVF- ICSI does not pose a higher risk of genetic abnormalities itself, except for those that would be attributable to the sperm delivered by the male.