Women are born with all the eggs they will have in their life – unlike men who produce sperm every day once they have reached puberty. Women’s egg reserves reach their peak about at about 25 years old before they decline slowly until age 35, with a rapid decline occurring after age 35 that partly explains the rapid fall in fertility at this age.
In addition to age, the egg count can be affected by many factors. Some women are genetically predisposed to having fewer eggs while others will acquire disease or other problems in their ovaries (such as endometriosis or ovarian cysts) that affects the number of eggs directly.
Some drug treatments such as medications used in the treatment of cancer or chronic problems such as arthritis or autoimmune disease may also affect both egg quantity and quality.
Lifestyle factors such as smoking may also affect a woman’s eggs, prematurely aging them up to 10 years. When planning your future fertility it is important to be aware of the factors affecting your chances of pregnancy and how much time you have for pregnancy to be an option.