Last updated January 2, 2024.
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Have you ever wondered, “How many eggs does a woman have?” If so, you aren't alone. Every woman is born with a specific number of eggs (which is her ovarian reserve) and ovarian follicles. Given that this is the case, a natural question might be: what determines how many eggs a female has?
In this blog, we're going to cover what you need to know about the female reproductive system. Get answers to all your burning questions about your biological clock—whether you're interested in learning more about woman's fertility or you'd just like to know “How many eggs are we born with?”
Before discussing a woman's egg reserve, it’s important to understand the basics of the female reproductive system. This system handles everything from ovulation to pregnancy and is an essential part of a woman’s anatomy. It also produces female sex hormones that allow the reproductive system to function properly.
The ovaries are two small organs that are on both sides of the uterus. These organs play a crucial role in the female reproductive system not only because they produce the egg cells, but they also store them until they are ready to be released. Once released, the eggs travel through the fallopian tubes where they can then be fertilized by sperm. Once the fertilization process has been completed, the egg will then travel to the uterus where it can be implanted on the thickened uterine lining. If the egg has not been properly implanted or if it was not fertilized by sperm, the uterine lining will shed itself, which is what you see during your menstrual flow.
If we're born with all the eggs we're going to have our entire lives, then why doesn’t our menstrual period start from birth? It's because our bodies wait until the reproductive system has developed enough to actually bear children. Puberty begins when the body starts producing large amounts of gonadotropin-releasing hormone (GnRH) in the hypothalamus. This hormone within the brain sends a signal to the pituitary gland to produce FSH (follicle-stimulating hormone), leading to a rise in estrogen levels—and the onset of puberty. (When testing fertility, doctors look at the FSH levels in the body as well as other hormones to see if it’s within a normal range for an individual’s age.)
There’s not a single answer to the egg quantity in a woman at birth. Why? Because everything comes down to individual genetics. That’s why there’s a lot of variation in how many eggs a woman is born with. In fact, it’s been estimated that—at the time of her birth—a woman can have anywhere between 35,000 and 2.5 million ovarian follicles (so it’s possible for one woman to be born with 50x more eggs than another woman!).
One of the key factors that affect your ovarian reserve today is how many eggs you originally had when you were born—which you can’t control or change because it's genetically-driven.
There’s another major player when it comes to the extent of your ovarian reserve. During each menstrual cycle, a proportion of your ovarian follicles are “recruited” to begin the ripening process. But generally speaking, only one ovarian follicle actually releases its egg—the rest of the maturing follicles (and their eggs) are broken down and can no longer be used. There’s good evidence that the number of follicles that are “recruited” each month varies depending on the individual. (Researchers have also found that a greater number of follicles are recruited in younger women.)
For example, in one woman, 100 follicles might undergo the ripening process, whereas in another woman more than 5,000 follicles could begin maturing during her cycle. Of course, if this so-called “recruitment rate” is particularly high, then one’s ovarian reserve will decrease more substantially.
As to what drives your ovarian follicle recruitment rate? The answer here, again, is genetics—a remarkable display of the power that genetics can wield in your health and wellness throughout all your life.
So what happens when a woman can’t get pregnant? As females age, a woman's egg count reduces—leading to a loss in reproductive potential. When a reduction in egg supply occurs, a woman may be experiencing diminished ovarian reserve (DOR). In most women, a diminished ovarian reserve occurs around the time of menopause; however, this can vary from person-to-person. In some cases, women in their 30s experience difficulties getting pregnant due to their egg quality and quantity. (Other factors, like Hashimoto's disease, can also affect reproductive health.) When a woman can’t get pregnant, fertility treatment options—like in vitro fertilization (IVF), egg freezing, and fertility drugs—can help.
Many women are concerned that their biological clock is ticking away, reducing the chances of pregnancy. So how can you check in on your body's reproductive health and fertility? A fertility specialist can run hormone tests, ultrasounds, and other tests to help assess egg quality and quantity. But you can also test several key aspects of your fertility from the comfort of home using an Everlywell test. The Women's Fertility Test measures 5 different hormones so you can see if your hormone levels are balanced to support normal ovarian function.
Whether you’re concerned about infertility or you just want to know that your egg supply is right on track, our at-home tests make it easy for you to get answers about your reproductive health quickly and conveniently.
Gleicher N, Weghofer A, Barad DH. Defining Ovarian Reserve To Better Understand Ovarian Aging. Reprod Biol Endocrinol. 2011; 9:23.