As more women wait to start families, it’s become a common concern to wonder about the health and quantity of their eggs. But is the number of eggs you have important? And how many eggs are women really born with?
It’s impossible to know exactly how many eggs you may have at this precise moment, because that number varies based on age, health, and other factors. But, reproductive scientists have determined the average number of eggs that most women start life with.
Surprisingly, that number’s an astounding 7 million eggs. At the five-month mark of gestation (that’s 20 weeks), a female fetus will have an estimated 7 million eggs. But by birth, that number has declined by nearly 30 percent, with just 2 million eggs left.
Fast-forward more than a decade to puberty, and by the time a girl begins menstruating, it’s estimated that she has only between 300,000 and 500,000 remaining eggs.
What happens to all those eggs?
Women are born with all the eggs they will ever have. Unlike men, who produce sperm throughout their entire lives, the female body cannot make new eggs. This means that once the bank of eggs (also called the “ovarian reserve”) is depleted, pregnancy is no longer possible.
From puberty through menopause, only one unfertilized egg is released at a time — which either culminates in pregnancy or menstruation. The ovaries of an average woman will release about 500 mature eggs in their lifetime. But, within the ovaries, about 1,000 eggs die each month despite the fact that they are safely tucked away and haven’t traveled through the fallopian tubes. Most of these eggs are immature, and are simply absorbed back into the body.
Eventually, your body will run low on eggs; at that point, the ovaries stop making estrogen, which triggers the beginning of menopause. Reproductive scientists have averaged that the normal age for menopause is 50, and at this point, most women can no longer get pregnant naturally. Any eggs that do happen to remain at this point will die and be reabsorbed.
How does age impact the number of eggs I have?
For a long time, the number 35 has been considered the age at which women see rapidly declining fertility, though that number isn’t set in stone, and is often misunderstood. Age does play a large factor in fertility, simply because as women age, the number of eggs they have quickly declines. That’s because the number of eggs that are reabsorbed by the body speeds up each year.
Reproductive specialists understand that female fertility slowly deteriorates through the 20s, but by age 30, the process quickens. At 35, the rate at which eggs decline in quality and amount is faster, and this speed quickens even further by age 40. By the time the average woman is 45, she has few viable eggs with menopause on the horizon in just five years.
While the quantity of eggs is decreasing, scientists know that the quality of eggs is doing the same. As you age, your eggs are more likely to have abnormal chromosomes, and the percentage of eggs with abnormalities increases.
So, when it comes to getting pregnant after age 35, the number of eggs in your ovarian reserve is important, but so is the quality of those eggs. For many women, being over 35 isn’t an issue at all when it comes to conceiving, while other women may have more difficulty. Even though age is important to consider, there are countless factors that play into successful pregnancy in your mid-30s or later.
How many eggs do I have left?
Unfortunately, there’s no surefire way to know how many eggs you were born with, how many you’ve lost, or how many are in your ovarian reserve right this second. However, there are several tests available that a reproductive specialist can utilize to get an idea how depleted your ovarian reserve may be. These tests can be used at any age, though they’re commonly targeted specifically to women over 35 who are trying to conceive.
Blood tests are the most common way to judge the status of your egg count. The anti-mullerian hormone (AMH) test is often used because, unlike other tests, can be done at any point during your fertility cycle. This test can also be performed if you are on hormonal contraception (which can impact other test results). The AMH test measures the amount of anti-mullerian hormone — a hormone that is made by follicles in the ovaries — in your blood. Generally, the lower the AMH, the fewer the eggs in your ovarian reserve.
Another blood test can measure the amount of follicle stimulating hormone (FSH) and estradiol. FSH helps with egg maturation in the ovaries, and is balanced by estradiol. If your FSH is high, you may have a lower number of eggs or have eggs of lower quality. Likewise, if the test returns high numbers of estradiol, your ovarian reserve may also be low, and remaining eggs may not be of the best quality.
A third test, called an antral follicle count, uses a transvaginal ultrasound to count the number of follicles. This test must be timed specifically to the second, third, or fifth day of your fertility cycle, when follicles are visible in an ultrasound. The number of antral follicles varies each month, and combined with hormone levels determined by blood tests, a doctor can use this information to estimate the number of eggs you may have.
When it comes to determining how many eggs you have in your ovarian reserve, no test is 100 percent accurate or perfect. But, these tests, along with other measures, can be helpful tools that aid you and your fertility specialist in determining how many eggs you may have left, their quality, and your course of action when it comes to having a baby.