age

There are lots of reasons why women are waiting longer to have children. Women are marrying later, waiting until their careers are on track, and are starting families in a second marriage. Thankfully, times have changed, and women who have children in their mid- to late 30s and 40s no longer draw negative stereotypes. But although attitudes have shifted, the facts haven’t. Even though research supports the safety of conception in women in later years, fertility inevitably diminishes with age. In fact, the decision to delay pregnancy may reduce your chances of successfully conceiving and/or delivering a healthy baby.

the decline of eggs

Fertility peaks in your early 20s and declines dramatically after age 35. So just what happens in the latter half of your thirties? Both the quantity and quality of your eggs are in sharp decline. As you age, the risk of producing an egg with genetic – specifically, chromosomal – problems increases. Many of these abnormal eggs will never fertilize or implant. But if one of these eggs beats the odds and you find yourself pregnant, there is a higher incidence of having a baby with a genetic disorder (such as Down syndrome) as well as miscarriage.

Before you are even born, your lifetime supply of eggs has been produced, with potentially seven million eggs resting in your ovaries. The immature eggs are immediately surrounded by a special layer of supporting cells and enter a resting state where they’ll remain until they resume growth. From this point forward, no new eggs are produced throughout your life.

As your eggs awaken from their resting state and resume development, a steady decline begins in the number of eggs in reserve in your ovaries. When you’re born, that number has already declined to about one million, and continues to drop to about 300,000 by the time you hit puberty. This gradual, steady decline continues throughout your reproductive life. Each month, several eggs will start developing further, but most will perish and only one or two eggs will actually ovulate. Eventually, you will exhaust your supply of eggs, which is when you’ll stop menstruating and become menopausal.

The chart below illustrates the decline in the number of eggs available in your ovaries, from before your birth to menopause.