Book an initial consultationThe new embryo is created by the fusion of a sperm cell with an egg. This process is called fertilization.
Fertilization can occur naturally in the woman’s fallopian tube or in the IVF laboratory with the help of assisted reproduction. There are two techniques for fertilization in an IVF laboratory: classic in vitro fertilization (IVF) or fertilization by micromanipulation of a sperm and egg, called ICSI (intracytoplasmic sperm injection).
Like any other biological process, fertilization is not perfect and sometimes fails: even if spermatozoa, like eggs, look completely normal and the assisted fertilization technique (IVF or ICSI) is technically flawless, in some cases fertilization does not occur. The measure of fertilization is the so-called fertilization rate, i.e. the number of fertilized eggs divided by the total number of eggs retrieved.
The fertilization rate for assisted reproduction (either classic IVF or ICSI) is 70-80% in modern laboratories – so it is considered very successful. Please note: However, this still means that 2 to 3 out of 10 retrieved eggs may not be fertilised!
Total fertilization failure (TFF) is when fertilization fails in all the eggs removed. While total fertilization failure is rare (1-4% of all patients), it is extremely frustrating for both patients and our fertility team. Unfortunately, our understanding of this phenomenon is still rudimentary. Risk factors for fertilization failure include an advanced age of the patient (>38) when only a small number of eggs can be retrieved, morphological abnormalities of the oocyte and poor sperm quality. Unfortunately, there is currently no diagnostic test that can predict TFF. TFF can occur repeatedly in the same couple.
There are several additional laboratory procedures that we can use to try to overcome fertilization failure:
– “Rescue” ICSI: application of the ICSI method the day after IVF if fertilization failure has occurred
– ‘Preventive’ (‘repeated’) ICSI: the use of ICSI in every future attempt, even in cases where traditional IVF fertilisation would otherwise be used
– Calcium ionophore as an adjunct to ICSI to initiate the fertilization process (studies have shown that increasing the concentration of calcium in the egg can increase the fertilization rate and can also favor the implantation of the resulting embryo)
– PICSI (physiological ICSI): modified ICSI, in which the most functional spermatozoa are more likely to be specially selected for intact genetic material before ICSI
Please note: All of the above additional procedures require informed consent and will only be used after thorough analysis of the case and in-depth discussion with patients.
Please note: There is no one hundred percent solution when it comes to total fertilization failure. Even if all the additional laboratory techniques proposed are used, there is a possibility that the (low) fertilization rate will remain unchanged.
We will be happy to explain further details to you in detail during your initial consultation.
