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Sunday, 11 May 2014

Immature eggs?

Anyone who has gone through IVF is likely to have come across this term: Immature eggs. When I say this to my patients during the course of IVF, many roll their eyes! It  is really not that complicated. As I had mentioned in my post on egg quality, eggs need to go through a reduction division of its genetic material in order to maintain normality. The big question is how do we know whether the egg has undergone this process?

The reduction division takes place in two stages. While the first stage is complete before fertilization, the second division only occurs after the sperm has entered the egg. 

At the end of the first stage, the egg splits into two cells each with one set of the two sets of chromosomes that are present to begin with. Normally, the division of the genetic material is equal but the cytoplasm (the cell fluid that surrounds the nucleus or genetic material) is divided disproportionately. The egg keeps almost all of the cytoplasm while the other cell - now called polar body has only a small amount.

A mature egg therefore looks like the picture given below. The small polar body is clearly visible. The absence of polar body means the first stage of reduction division is not complete and this egg cannot be used to make embryos for the fear of forming embryos with more than normal amount of genetic material.  

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