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Fertilization Failure

Fertilization Failure

Total fertilization failure (TFF), which is the failure of fertilization in all oocytes after IVF. The commonest cause of failed fertilization after IVF is abnormal sperm. This could be because of abnormally shaped sperm; or sperm dysfunction. In some cases, this may result in total failure of fertilization.

However, even after ICSI, not all the eggs will fertilize. This is because some of the eggs are immature. Mature eggs are in metaphase II (M2). As eggs mature, they go through stages of chromosomal division called meiosis, which halves their chromosome number. The extra chromosomes are contained in a small, round body located on the side of the egg called a polar body. If an egg does not have a polar body at the time of the fertilization check, this means it is still immature, and will not allow the sperm to fertilize it.

Reasons Eggs Fail to Fertilize

The reason behind failed fertilization after ICSI is not a technical one; there are a few factors that could explain the lack of fertilization:

• The egg may not have survived after the injection. This could occur if the eggs are post-mature or if they have just matured prior to ICSI. It could also indicate poor egg quality.

• The sperm head may not have decondensed, which would cause failed fertilization due to the DNA of the sperm remaining ‘locked’ in the sperm head. This would cause failed fertilization or abnormal fertilization.

• The egg may not have been activated and didn’t participate in the intracellular steps of fertilization. Failure of egg activation is one of the most common reasons for failed fertilization after ICSI.