Fertility is one of the most natural aspects of human biology, yet it is also one of the most influenced by age. For women, the connection between age and fertility is especially significant because of the way the ovaries and eggs develop, mature, and decline over time. Understanding this relationship is key for women making decisions about family planning, reproductive health, and lifestyle choices.
How Many Eggs Does a Woman Have?
Every woman is born with a fixed number of eggs. Unlike men who produce new sperm throughout life, women cannot create new eggs. At birth, a baby girl has about one to two million eggs stored in her ovaries. By the time she reaches puberty, this number reduces to around 300,000–400,000. Out of these, only about 300 to 500 eggs will be released during her reproductive years. The rest naturally degenerate over time, a process known as atresia.
Decline in Egg Quantity with Age
Egg quantity begins to decline gradually in a woman’s 20s but becomes more noticeable after the age of 30. By age 35, the decline accelerates, and by 40, the number of eggs left is significantly reduced. This decline is natural and unavoidable, and it directly impacts fertility. Even if a woman is healthy, exercises regularly, and eats well, the number of eggs will continue to decrease with age.
Egg Quality and Chromosomal Health
Fertility is not only about the number of eggs but also their quality. Younger women tend to have healthier eggs with fewer chromosomal abnormalities. As women age, the chances of chromosomal errors in eggs increase, which raises the risk of miscarriage, infertility, or genetic conditions such as Down syndrome. By age 35, both egg quality and chromosomal stability begin to decline more sharply, which explains why pregnancy complications become more common with advancing maternal age.
Fertility Timeline
- 20s: Fertility is at its peak. Eggs are abundant and usually of high quality. Pregnancy rates are higher, and risks of miscarriage or genetic abnormalities are lower.
- Early 30s: Fertility remains relatively strong but begins to decline slowly. Many women can still conceive naturally without significant difficulty.
- Mid-to-late 30s: Fertility declines more quickly. Both the number and quality of eggs reduce, making it harder to conceive. Risks of miscarriage and genetic abnormalities increase.
- 40 and beyond: Fertility is significantly reduced. Natural conception becomes less likely, and if pregnancy occurs, there is a higher risk of complications. Assisted reproductive technologies such as IVF may be needed, often with donor eggs.
Impact of Lifestyle and Health
While age is the biggest factor affecting fertility, lifestyle and overall health also play an important role. Smoking, obesity, excessive alcohol use, untreated medical conditions, and chronic stress can speed up the decline of egg quality and fertility. On the other hand, maintaining a healthy lifestyle may help protect egg health to some extent, though it cannot stop the natural decline that comes with age.
Fertility Preservation Options
For women who wish to delay childbearing, fertility preservation methods such as egg freezing (oocyte cryopreservation) are now widely available. This process involves retrieving healthy eggs at a younger age and freezing them for future use. Although not a guarantee of pregnancy, it offers a way to improve the chances of conception later in life.
Final Thought
A woman’s age plays a decisive role in her fertility, affecting both the number and the quality of her eggs. While modern medicine has advanced to support women who want children later in life, nature still favors younger age when it comes to reproduction. The best approach is for women to be informed, consider their personal goals, and seek medical guidance early when planning their reproductive journey.
