the ferteve library

Women are born with nearly 2 million eggs, so what on earth happens to them all?

27th August 2024

Ageing affects every part of our bodies, and our ovaries are no exception. We’ve known for a while that we lose a significant number of eggs to age. However,  a study published in 2010 took everyone by surprise when they showed us in numbers exactly how fast this decline might be occurring. They developed a mathematical model that showed that for 95% of people with ovaries, 88% of the ovarian reserve (eggs they’re born with ) is already gone by the age of 30 years, and by the time they hit 40 years, 97% of the reserve is gone. An important caveat to consider here, the number of eggs you have is not the only indicator of fertility (and on its own, it can’t tell you whether or not you can conceive). However, knowing more about your egg reserve and how it declines, can help you make better-informed decisions about your reproductive timeline.

The Biological Clock: What Happens as Ovaries Age?

People with ovaries are born with a finite number of eggs, approximately one to two million. By the time you reach puberty (which is when your periods start), the number of eggs you have has already reduced to 300,000 to 500,000. This is thought to be due to a process called atresia, which is a natural process through which follicles (sacs that house the eggs) degenerate and die. Interestingly, only a fraction of these remaining eggs, around 400-450, will ovulate during a woman's lifetime.

The decline in egg quality is often a forgotten aspect of ovarian ageing. As women age, the likelihood of chromosomal abnormalities in eggs increases, which can lead to failure to fertilise, implant, miscarriages, and congenital disabilities. The decrease in both the quantity and quality of eggs contributes to the increasing difficulties women face, to conceive, as they get older.

Factors Influencing Ovarian Ageing

While age is a primary factor in declining ovarian reserve, several other elements can influence this process:

Genetics: A woman's genetic makeup can determine the rate at which her ovarian reserve declines. Women with a family history of early menopause may experience accelerated ovarian ageing.

Lifestyle Factors: Smoking, excessive alcohol consumption, and obesity can negatively impact ovarian function. Smoking, in particular, is associated with reduced ovarian reserve and earlier onset of menopause.

Environmental Factors: Exposure to certain chemicals and toxins can impact ovarian function and accelerate ageing.

The Role of Oxidative Stress in Ovarian Ageing

Oxidation is a normal and essential process that happens in your body. Oxidative stress is what occurs when there is an imbalance between free radicals and antioxidants in the body, leading to cellular damage. The ovaries are particularly susceptible to oxidative stress due to their high metabolic activity. While there is a need for the production of reactive oxygen species (ROS) during follicular development and ovulation, an abnormal increase in ROS can speed up ovarian damage.

Oxidative stress can accelerate the depletion of the ovarian reserve and negatively impact egg quality. It can cause DNA damage in oocytes, leading to chromosomal abnormalities and reduced fertilization potential. Antioxidant defence mechanisms weaken with age, making older women more vulnerable to oxidative damage.

Strategies to mitigate oxidative stress include adopting a diet rich in antioxidants, such as fruits and vegetables, and minimising exposure to environmental toxins. Research is ongoing to explore the potential of antioxidant supplements in preserving ovarian function and improving fertility outcomes.

The Decline of Fertility: A Timeline

Your fertility is typically at its peak in your early 20s to late 20s. During this period, the likelihood of conception is maximum, and the risk of miscarriage and chromosomal abnormalities is relatively low. However, fertility slowly begins to decline in the early 30s, with a more pronounced decrease after age 35. By the age of 40, the chances of conceiving naturally drop significantly, and the risk of complications such as miscarriage and genetic abnormalities increases.

Understanding this timeline is beneficial if having children is part of your plan. If you wish to conceive later in life, you should be aware of the potential challenges and consider options such as egg freezing or assisted reproductive technologies (ART).

How can I optimise my ovarian health?

While ovarian ageing is a natural process, there are steps you can take to optimise their fertility

Healthy Lifestyle: Regular exercise, a balanced diet, and maintaining a healthy weight can positively impact ovarian function.

Avoiding Harmful Substances: Reducing exposure to harmful substances such as tobacco, alcohol, and environmental toxins can help minimise ovarian damage.

Regular Check-Ups: Regular proactive fertility and hormone testing can help monitor reproductive health and identify potential issues early. Tests such as AMH levels, FSH and antral follicle count (AFC) can provide insight into your ovarian reserve.

Fertility Preservation: For women who wish to delay childbearing, options such as egg freezing can be a good way to do that. This involves retrieving and freezing eggs at a younger age for future use.

The Emotional Impact of Ovarian Ageing

Knowing that you’re racing against time when it comes to your fertility can be emotionally tough. Luckily science is advancing and opening more doors along the way. Mapping your family planning goals, proactively testing (fertility and hormone tests ) to understand where you stand and re-evaluating yearly can help you make better, more informed choices to help you achieve everything you’ve pictured for yourself on your terms.