Today we talk about what happens to the unfertilized egg. I'm Doctor Mark Amos and this is taco. About fertility Tuesday. So there's this question that I get asked a lot of time and the first time I heard it I thought it was kind of a silly thought. And then over the years I've had a lot of people ask this question and then I started realizing that it's actually a very common thought. And that is, when an egg's not fertilized, what
happens to it? Have you ever wondered what happens to that egg if it doesn't meet a sperm? What happens if your tubes are tied and the sperm can't get to it? Does it affect your menstrual cycle? This question, or thought was more about the guy thought when a woman has a menstrual cycle that is her eggs coming out of her body. He thought since her tubes were blocked, he was not sure what's going on, why she
gained a period. And again, when I first heard this I thought, he's a guy and we're not that smart anyway, so that's probably why he thinks that. But then I've had women ask that. I've had many women after they lose their tubes go, am I going to still get my menstrual period? And I think, why wouldn't you get your menstrual period? I thought maybe they misunderstand the tubes, that maybe they thought by the tubes
being blocked that maybe thats how the flow comes out. But then when I asked the next questions to figure this out, the thing they kept saying to me was, oh, I thought what comes out are the eggs. Thats what your menstrual cycle is. And that was fascinating to me because ill be honest, even before medical school I actually understood that a little bit more through sciences and stuff that it was
the uterus that was shedding. But what I realized is this is a very common question, the question of what happens to that egg when it doesn't meet sperm, it doesn't become fertilized. So let's start first with a premise that your period is not the eggs coming out. Now I understand why people can think that because technically if the egg gets picked up and then it goes down the fallopian tube in the uterus, well obviously it's going to come on out when you have your period. But
if your tubes are blocked, you still get a period. So I see where that comes from. But what the menstrual cycle really is, is the inside of the uterus is building up through the month, and as it's building up, it's getting ready for implantation. And if that implantation doesnt occur with a fertilized egg, then its being shed out and well get into that in a minute. But at least first part were going to say is the menses is not the eggs coming out, its the uterine lying,
shedding. So lets start with the first part, the egg. So every month your body has multiple follicles that grow. Those follicles are these sacs that have an egg in it. Now, your body naturally makes just one that releases, but there's actually 1000 eggs that are selected. And from those thousand, somewhere around eight to maybe 20 start to grow, and then those eight to 21 is selected to be released. Whereas in other animals, like cats, multiple of these follicles are
released. But in humans, it's just usually one egg per month. But when you get twins, which are fraternal, that's the situation where you release two. Now, this process happens regardless if you're trying to get pregnant. That's why women have menstrual cycles. Now, when you release an egg, that sac that's left over from where the egg released closes and becomes a corpus luteum, which is basically a progesterone factory that makes progesterone to support a potential
pregnancy. Now, if that egg is fertilized, that egg will keep working its way down the fallopian tube while it's fertilized, become an embryo. That embryo will then implant into the lining of the uterus that's been building up through the month. And then that embryo will start making hcg, which comes from the syncidiotrophoblastic cells, which are part of the placenta, that signal goes back to the corpus luteum and tells it, hey, stick around,
I need your progesterone for a while until I can make my own. And that's exactly what happens. The baby sends back the ECG, the corpus luteum keeps making progesterone, and the pregnancy keeps moving forward. So that's the normal way things work. But what if the egg never met sperm, which can happen some months even when you're trying to. Well, that egg is still going to be picked up by the fallopian tube, and that egg is then going to work its way down the fallopian tube into the
uterus. But where things are going to go different is that because that egg never fertilized, its never going to make hcg. And since it doesnt make the hcg levels go up, the corpus luteum only has a finite time of life. That corpus luteum will collapse after about twelve to 14 days. And when it does, the progesterone levels will drop. And at that point, thats when you will shed the lining of the endometrium, which is the inside of the uterus, because the progesterone is
no longer supporting it. That is why it drops out. So from a technical standpoint, yes, when the woman has her menses, there is an egg in there. And technically, if she released more than one egg, there is more than one egg in that menstrual cycle being released, but most of the eggs never get there. Of, those thousands of eggs that shes going to lose that month that were selected, most of them never even
grow. And of the ones that grow, only the ones that are released are the ones that will be in that menstrual cycle. So in reality, the menses is basically just endometrial lining being passed, and that only a microscopic egg, which, if it wasn't fertilized, is already degenerating, is being passed with the menstrual cycle. This cycle of menstruation occurs approximately about 450 times in the woman's lifetime, and they usually have about 400 chances of ovulation to get pregnant.
The discrepancy between those numbers is the fact that women start menstruating, sometimes very early, before they're even having intercourse. And as women get older, after 44, 45, the chances of getting pregnant are very low. So there is a portion of their life where they're having the menses, but really can't get pregnant. Pregnancy really falls into that, about 380 to 400 ovulations through your lifetime.
That's actually one of the ways fertility doctors are able to improve pregnancy rates, is by making more eggs, you're getting more chances per ovulation. Naturally, you only get twelve chances a year to get pregnant. But if you're making an extra egg every month now, you have up to 24, chances in a year because you're making two eggs, and potentially even more with other fertility
treatments. So, based off of what we talked about, even if a woman's tubes are blocked, she's still going to have amenses, because it doesn't matter if the egg makes its way down to the uterus, the egg's not fertilized, which means it's never going to make hcg. And so the, hormonal drop is what's going to cause her to get her menses, not whether the egg made it
to the uterus. A slight tangent to this topic, but still relevant is this question about when you go through fertility treatment then, and you're making more eggs, will you then go into menopause early? Will you lose, the number of eggs you lose every month will go higher. And the answer is no, because as I discussed, you're going to lose 1000
eggs pretty much every month. And the eggs that we're removing from your body or that we're making to ovulate extra are the same eggs that were going to be lost anyways. All women have a natural decline in their fertility reserve as they get older. It's called a process of atresia. And by age 35, most women only have 6% of their egg reserve remaining.
So what happens at that point? There is a big tipping point at which there is higher miscarriage rates, lower fertility, because now the rate is so much lower and the quality of eggs goes down more. Now, one interesting question came up from someone was what if you dont have a uterus, what happens to the egg after its
ovulated? Thats a great question because again, if you were under the impression that the only way the egg got out was through the uterus and that was the menses, then itd be this idea theyre building up somewhere in the body, but in reality, the egg is still released, it would not be fertilized. And after that 24 hours, that egg will undergo that atresia process and will still die. And then it will fall somewhere into the pelvis and be reabsorbed into the lining of the
abdomen. Well, I know I didnt uncover and unravel the eggs essential question of the universe tonight. Hopefully this was a helpful episode to some. Maybe you had the same question. And if you found this episode helpful, as always, share it with a friend who it might benefit. And if you like the podcast, as I always say, please give us a five star review on your favorite medium. As always,
please come back again. I really look forward to talking to you guys again next week on Taco Bell fertility Tuesday. Subscribe M.