Why is female age such an important determinant of fertility potential?

Since no new eggs are produced after birth, a woman’s eggs age as she ages. Eggs therefore succumb to ageing effects along with other cells in the body. For eggs, these ageing effects occur surprisingly early, around the mid-thirties. Based on the critical importance of egg quality and its close relationship to age, the most important predictor of fertility potential is therefore female age.

In contrast to women, men retain a reservoir of sperm-producing cells (known as germline stem cells) in their testes allowing them to produce new sperm throughout their lifetime. As a result, and although age does affect sperm quality to some extent, the effects of ageing are far less severe for men than for women.

To put this in perspective, a 45-year-old patient who is ovulating, has healthy tubes and whose partner has normal sperm, has all the natural fertility requirements in place but has relatively low fertility potential due to low egg quality. In contrast, a 26-year-old patient with normal tubes and normal sperm but who is not ovulating, has limited natural fertility because of not releasing an egg. However, due to her young age, her fertility potential is high so that with appropriate treatment she has a very good chance of achieving a successful pregnancy.

Professor Homer is an internationally leading expert in egg quality and the effects of ageing. He has received millions of dollars in research funding from the NHMRC to study egg quality. Using this funding, his lab is actively researching novel treatments for reversing poor egg quality. Click here to read his recent paper on the effect of ageing on egg quality published in the world’s top reproduction journal.