Does Being on the Pill Improve Egg Stores?

I understand that the number and quality of eggs goes down with age. I was also on the pill for a long time (about 10 years) a long time ago. I’d hypothesize that not ovulating for 10 years would improve my egg stores later in life. Has anyone researched this connection? Most articles I’m seeing are about fertility immediately following birth control, not the long-term effects.

—Anonymous

Unfortunately, being on birth control does not improve egg stores.

Most of the data for this comes from our understanding of ovarian development and aging.

Women are born with a finite number of eggs, and those eggs are lost over time. In fact, the decline in egg numbers starts even before birth. The number of eggs peaks at about 6 million around 20 weeks gestation. At birth, that number has decreased to about 1.5 million eggs; at puberty, that number is about 500,000. After puberty, about 1,000 eggs are lost monthly, and the decline becomes more rapid after age 35. Menopause is the loss of functional eggs.

We don’t completely understand this process. What we know so far is that eggs have various stages of development, and there is loss as they progress through each stage. Birth control works by decreasing the hormones that drive the growth of late-stage eggs. But it is estimated that only about 0.1% will ever be ovulated; the rest degenerate.

So, much of this is happening well before and outside of ovulation. However, studies have tried to understand the effect of birth control on anti-Mullerian hormone (AMH), a measure of how many eggs a woman has.

This study looked at the AMH levels of about 1,600 women and found that women who were current users of birth control had lower AMH levels compared with non-users, and there was little difference in AMH levels between former users and non-users. Birth control lowers AMH levels the same way it inhibits ovulation: by decreasing levels of hormones that drive the progression of eggs to ovulation.
Still, keep in mind that egg quality matters more than egg numbers.