The Fertility Triangle: Egg Quality and Quantity

The use of this triangle is to simplify the explanation of the ovarian reserve and its use in clinical practice. We are well aware of AMH is being a marker for ovarian reserve which comes from the small pre-antral, pre-antral and the small antral follicles. The antral follicle count is a visible indicator of the ovarian reserve and relevant to stimulation. Whilst the AMH also tells us about the inhibitory control of the follicles, the antral follicles tell us the response of the follicles to hormonal changes.

In the figure the bottom half of the triangle is indicated by the pre-antral follicles which predominantly secrete AMH. The middle part of the triangle is by the antral follicles which are divided into the large antral follicles and the small antral follicles. These antral  follicles which are more receptive to stimulation and will respond to hormonal stimulation. Finally in the top of the triangle is the role that the ovary fulfils which is to have a dominant follicle.

The follicles move from the pre-antral zone to the small and finally to a large antral follcile . There is evidence that this is a continuous phenomena with the antral  follicle counts changing. At the same time there is an invisible loss  from the small Piri antral and the pre-antral follicles indicated by the decline in AMH . Thus the AMH declines first as the woman starts ageing.

At the site of the antral follicles ,the small antral follicles are more likely to go into atresia or  be recruited at a later part of the cycle. Large antral follicles have less inhibited control  of AMH and are more likely to respond to stimulation. Follicles that go into atresia at this stage we call is visible atresia.

Thus by reviewing the antral follicle count and measuring follicle counts of more than 4 mm and those which are less than 4 mm we can divide the antral follicle into smaller the last both of which respond differently to stimulation. The AMH tells us to a large extent about the inhibitory response of the ovary and how easy or difficult stimulation would be. Often for women it is the antral follicle’and the variations in the  follicles that matters at stimulation rather than AMH.

It is important to note that age alone is the best indicator of quality while the antral follicle count and the AMH tell us more about quantity.