Ep 245: Understanding Your Menstrual Cycle

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In this episode you're going to learn exactly what happens during your menstrual cycle. I decided to talk about this because, quite frankly, it’s something that many of us don’t fully understand. We talk about our cycles in relation to pregnancy but there’s a lot more to periods than ovulation!

Your cycle can influence so many aspects of your life: libido, mood, energy, skin, appetite, and more! Better understanding your periods can help you make informed decisions regarding reproductive health, fertility, and overall well-being.

In this Episode, You’ll Learn About:

  • What constitutes a regular menstrual cycle
  • What the phases of the menstrual cycle are
  • Which hormones are associated with pregnancy
  • When ovulation occurs
  • How to track ovulation
  • How fertilization and implantation work
  • How IUDs prevent pregnancy
  • Whether you can really have a period while you’re pregnant

Links Mentioned in the Episode


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Dr. Nicole (00:00): In this episode, I'm going to help you understand your menstrual cycle.

(00:11): Welcome to the All about pregnancy and birth podcast. If you're having a baby in the hospital, you are giving birth in a system that too often takes away power from women over what happens in their own bodies. I'm Dr. Nicole Calloway Rankins, a practicing board certified OBGYN, who's had the privilege of helping well over a thousand babies into this world. I've been a doctor for over 20 years, and I'm here to help you take back your power, advocate for yourself, and have the beautiful pregnancy and birth that you deserve. This podcast is for educational purposes only, and it's not a substitute for medical advice. Check out the full disclaimer at drnicolerankins.com/disclaimer. Now, let's get to it. Hello there. Welcome to another episode of the podcast. This is episode number 245. Whether this is your first time listening or you've been here before, thank you for spending some time with me today.

(01:05): In this episode, I am going to break down exactly what happens in your menstrual cycle. I decided to talk about this because quite frankly, it's something that many of us don't really understand. We talk about menstrual periods or the medical term is menstruation. I hate saying that word. It sounds weird, but menstruation and in relation to pregnancy or getting pregnant, we talk about ovulation, but we don't necessarily talk about how those things connect and the pieces that happen in between. So I'm going to break all of that down for you today. It's also important to know about your menstrual cycle because it can potentially influence other things in your life. Like some women experience changes in libido during different phases of the menstrual cycle. Some women have different energy levels during different phases of the menstrual cycle with increased energy around ovulation fatigue during your period.

(02:06): The menstrual cycle hormone changes can impact your mood, can impact your emotions. They can sometimes lead to PMS, which is premenstrual syndrome or mood swings and irritability. You can have skin changes related to your menstrual cycle like oiliness, acne, skin sensitivity. Some folks have changes in their appetite or food cravings during different phases of the menstrual cycle. You may even have breast sensitivity depending on where you are in your menstrual cycle. Now, of course, individuals, you will each have your own unique experience and not everyone will notice changes in all of these aspects of their health related to their menstrual cycle. Also, we know that there are factors like stress and your lifestyle that can influence some of these things as well. But you're not going to know if there's an association if you don't understand your cycle. And if you don't track your cycles and track your symptoms, it can help you better understand your unique patterns and help you make more informed decisions regarding your reproductive health, your fertility, and just your overall wellbeing.

(03:16): So with that being said, we are going to dive into the menstrual cycle. But before we get into that, when you have your menstrual cycle and if it ends in a pregnancy, then something you're going to need to do is get ready for your birth with childbirth education, and that's where the birth preparation course comes in. The birth preparation course is my online childbirth education class that will get you calm, confident, and empowered to have the beautiful birth that you deserve. It covers everything from getting in the right mindset for your birth, to understanding all of the details of labor and birth and what's happening in your body, possible things that can occur, labor induction, how to manage pain, how to get off to a great start postpartum, how to make your birth wishes. Just some really great information folks. Love, love, love the course.

(04:03): You can check out all the details at drnicolerankins.com / enroll. Okay, so let's start off with what is the menstrual cycle. So your normal menstrual cycle is a really tightly coordinated cycle between the pituitary gland. That's a little tiny pea-sized gland in our brains that secretes hormones, for example, that secretes oxytocin. It's a coordinated cycle between your pituitary, your ovaries, and your uterus. It's actually a pretty magnificently coordinated cycle, and I think it's just kind of amazing that this happens month after month after month, and that tightly coordinated cycle results in the release of a single mature egg from a pool of hundreds of thousands of eggs. Okay, so that happens with every single regular normal menstrual cycle. So what exactly constitutes a normal menstrual cycle? Well, we talk about four things to define what is a normal menstrual cycle, and that's going to be frequency, regularity, the duration, and the volume.

(05:16): So for frequency, the normal frequency of your menstrual cycle is defined as from the first day of one period to the first day of the next period. Okay? So day one is the start of your period. When you have your period again, then it resets, and that's day one. So the normal frequency in the onset of your menstrual bleeding or your period is every 24 to 38 days. So that's the frequency every 24 to 38 days. And then we look at regularity. We look at the number of days between those periods, so that can actually vary. Okay? When you're between 18 and 25, your cycle can vary by around nine days and still be considered normal. So for instance, one month, your menstrual cycle might be 25 days. The next month it may be 30 days. That is considered normal. There's a little bit less cycle variation when you're in your middle years.

(06:20): So between 26 and 41, typically it's going to stay within seven days. Okay? So if you had a cycle that's 24 days, one month, and then it's to get to the next one is 34 days, that would be a little bit longer and atypical. If you're between 26 and 41, typically it's going to be within seven days, and then between 42 and 45, it's back to roughly being nine days. So it can vary. So again, frequency every 24 to 38 days and regularity, that number can vary about anywhere from seven to nine days when you're younger than 18 and older than 45. It's just really hard to predict because ovulation is all over the place, so your cycles can be all over the place. Now, as far as duration, the number of normal days that is considered normal in a single period is eight days or less.

(07:15): So if you are bleeding for more than eight days, then that is considered abnormal. There is no lower limit to this. So there's not like if your period is only a couple days that that's a problem because there's nothing that's associated with having a shorter period. By nothing, I mean no medical problems or pathologic conditions that are associated with a shorter period. So there's no lower limit. But if you are bleeding more than eight days, then that is considered a problem also regarding the volume of your period or your menstrual blood. And right here I'm talking about, I should back up and say, these are the things that are associated with not just your menstrual cycle, but also your period, which is part of that cycle, and I'm going to get into that in just a minute. But the volume is really subjective by volume is how much you bleed.

(08:07): So we define a problem as if it's a problem for you. So if it's interfering with your physical feeling, like how you're feeling, if you feel tired, if you feel fatigued, if it's interfering with your social life or your emotional wellbeing, then that is a problem. Like if your periods are so heavy, you're bleeding through your clothes or you're anemic, then that is a problem, but it doesn't necessarily have to show up in blood work. If it's enough that it's interfering with your daily life and your functioning, then that's something where we should look at and do something about so that you can feel better. And when we look at research to measure blood loss, or when research studies look at menstrual periods and menstrual blood loss, the definition of normal is less than or equal to 80 milliliters of menstrual blood loss per cycle.

(08:55): That's about three ounces of blood per cycle. So not a huge, huge amount, but that's really only for research purposes. We're not going around and measuring in a cup or anything how much bleeding we're having during our periods. It's really about if it's a problem for you, then that's something that needs to be addressed. Okay? Now, when we look at the menstrual cycle, it's divided into two phases. Those two phases are the follicular phase and the luteal phase. The follicular phase begins with the onset of your period. So the first day of your period, that is the beginning of your menstrual cycle, that is the beginning of the follicular phase. And the follicular phase ends on the day before what's called the LH surge, the luteinizing hormone surge, and that LH surge is what triggers ovulation. Now, the luteal phase, the second half of this cycle begins on the day of the LH surge, and then it ends at the onset of the next period.

(10:03): Alright? So follicular phase is the first half, the luteal phase is the second half, and let's break those down even further. So the follicular phase is really all about maturing an egg, getting an egg to grow. So during the follicular phase, the pituitary gland releases follicle stimulating hormone. That's FSH. And what happens is that FSH stimulates the growth and development of several what's called ovarian follicles, okay? These ovarian follicles contain an immature egg or ohoh site. Now, these follicles, once they are stimulated by FSH, they produce estrogen, and as they mature, they produce more estrogen. So as the ovarian follicles grow, produce estrogen, then these rising levels of estrogen do something called negatively feed back to the pituitary. And what that means is that as the estrogen levels go up, that sends a signal to your pituitary to slow down the release of FSH, okay?

(11:28): And it does that in order to prevent the excessive development of follicles. The way the human body is designed female body, it's really to release one, maybe two eggs at a time and not more than that. And so it's a tightly coordinated system that keeps it to only developing and maturing one or two eggs at a time. So again, that FSH is secreted, it stimulates the ovaries, the estrogen goes up, that sends a signal back to the pituitary to slow down the FSH. So there are not too many follicles that are developed now, eventually, and we're not exactly sure what causes one follicle to be dominant, but one dominant follicle will emerge from the follicles that were being stimulated, the others will degenerate, and then that dominant follicle continues to produce increasing amounts of estrogen. Now, once the estrogen gets to a certain level, then it actually flips from a negative feedback to a positive feedback effect on the pituitary.

(12:42): And what that positive feedback triggers is a surge in another hormone called G luteinizing hormone or lh LH secretion from the pituitary. And the LH surge is the signal for the mature follicle to release the egg from the ovary, a process that you know and I know as ovulation. Alright, so I hope that makes sense. Okay, so just to recap that part of what happens in the follicular phase in the ovaries, FSH from the pituitary stimulates the ovaries to recruit follicles. One dominant follicle emerges that estrogen feedback causes it not to produce too many follicles, and then that estrogen gets to a level where it causes LH to be secreted, and that LH surge triggers ovulation. I'm going to talk more about ovulation in a minute, but first, let me tell you what's happening with the uterus in the follicular phase. So in the follicular phase, in the uterus, again, that is the start of your period.

(13:50): So your first day of your period is what starts the follicular phase. And what's happening in your uterus is the shedding of the uterine lining from the previous menstrual cycle when you didn't get pregnant. Okay? So what your period is, it is the shedding of the lining that was built up from the cycle before and you didn't get pregnant. So your body realized, Hey, we need to get rid of this old lining and we need to start fresh. That is what is expelled as menstrual blood. So as the follicular phase progresses, it starts off with your period, you have your period, the phase continues, and roughly each phase lasts about 14 days. So roughly the follicular phase and luteal phase last about 14 days. So as the follicular phase progresses, the levels of estrogen rise, okay? Again, that's being produced by the ovarian follicles. So it's stimulating the growth and the thickening of the endometrial lining of the uterus.

(14:55): Okay? So all of that estrogen is helping to rebuild the lining of the uterus to prepare it for a potential pregnancy. So there's blood vessels, there's glands happening. It's all about recruiting an egg, okay? Also, in the follicular phase, the cervical mucus becomes more receptive to sperm. It's getting that egg ready, getting ready for a possible pregnancy. That cervical mucus creates a more favorable environment for sperm survival and transport through the cervix. Okay? This is all part of the uterus getting prepared for a potential pregnancy. The uterus is getting ready to receive a fertilized egg. If ovulation leads to conception, that's what's happening in the follicular phase, maturing that egg, getting the uterus ready. Now, as I mentioned before, as the follicular phase progresses and those estrogen levels rise, when it reaches that certain threshold, it triggers that positive feedback mechanism to the pituitary, and it's a sudden surge.

(16:11): It's a burst of lh, of luteinizing hormone. If you look at a graph, it's like a big spike of LH hormone, and that surge is the signal to that mature ovarian follicle, that dominant follicle to release the mature egg. This is ovulation or follicle rupture. It literally burst out of the ovary. It's released from the ovary and enters the fallopian tube where it can potentially be fertilized by sperm. Alright? Now, ovulation typically occurs around the middle of the menstrual cycle around about day 14, but it can be very a bit, but roughly the follicular phase is halfway through, and then there's ovulation and the rest of the cycle, it can vary based on stress, illness, lifestyle, but roughly it's going to be about 14 days before the start of the next period. And your fertile window is actually quite small relative to the link of your whole menstrual cycle.

(17:12): So the fertile window is when you can actually get pregnant, and it's the days leading up to ovulation and then the day of ovulation itself. Sperm can survive in the female reproductive tract for several days, and then the egg can be fertilized for only about 12 to 24 hours after ovulation. So the total fertile window are the days leading up to ovulation when sperm can just hang out and wait for the egg. And then the day of ovulation, and that's usually around five days. Okay? So your fertile window is going to be five days, including the day of ovulation, and then the few days before, ways to detect that fertile window. As an aside, ovulation predictor kits pick up that LH surge, so they pick up that big spike in LH luteinizing hormone. It shows up in your urine. That's what opk or ovulation predictor kits look for.

(18:09): So it's going to tell you just before you're ovulating that you've had that surge that's about to trigger your ovary to release that egg. Some other ways you can track your fertile window or basal body temperature. Your temperature rises ever so slightly after ovulation. You have to get a special thermometer in order to accurately track it because it's accurately track it, because it's just a tiny change in your temperature. It can help you estimate the timing of ovulation or help you understand your fertility awareness. Also, cervical mucus will change around ovulation. Cervical mucus becomes slippery, stretchy, creating a more favorable environment for sperm. Okay, so that is the follicular phase and ovulation, and then we move into the luteal phase. So the luteal phase again is just hitting the gas on, preparing for a potential pregnancy. Okay, just all going, all in on getting ready for a pregnancy.

(19:13): So after ovulation, the ruptured follicle transforms into what is called the corpus lium, and that is influenced by the LH D luteinizing hormone. The corpus lutetium is actually a temporary gland that primarily produces progesterone. It does produce some estrogen, but it primarily produces progesterone. So every month you're making this temporary gland in your ovary. Now, progesterone levels rise significantly during the luteal phase. They reach their peak about a week after ovulation, and progesterone plays a crucial role in preparing the lining of the uterus for potential implantation of a fertilized egg. This is why we supplement with progesterone in the early part of pregnancy for people that have early pregnancy loss, because it plays a really important role in getting the uterus ready. So under the influence of progesterone, the endometrial lining, that's the lining of the inside of the uterus, endometrium inside of the uterus are the same thing.

(20:28): The lining becomes thick, it becomes more vascularized with blood vessels, it's enriched with glands. And these changes create a nice supportive environment for a fertilized egg to implant settle in and establish a pregnancy. And then not only that, but progesterone also inhibits further ovulation during the luteal phase, preventing the release of additional eggs that also suppresses the secretion of FSH, that follicle stimulating hormone from the pituitary gland, which prevents the development of new ovarian follicles. The body just really created this coordinated system of really focusing on releasing just one egg a month, not having multiple eggs in the mix, just one egg during your menstrual cycle, roughly a month. Okay? Now, during the luteal phase, your cervical mucus will become thicker and it will also become less receptive to sperm. This is another protective mechanism to reduce the likelihood of additional sperm entering the uterus after ovulation has occurred. So really, the body just creates this small window for potential pregnancy.

(21:54): Now, fertilization in implantation do not occur, and I'll talk about what those are in a little more detail in just a second. So if fertilization doesn't occur, implantation doesn't occur, then the corpus lutetium begins to degenerate towards the end of the luteal phase. And as the corpus lutetium breaks down, then progesterone levels decline, and the decrease in progesterone levels then triggers the breakdown of the uterine lining, and that leads to the onset of your period and marks the beginning of the next menstrual cycle. What happens during fertilization and implantation? So fertilization, if the egg is fertilized, fertilization typically occurs in the fallopian tube. The sperm meets the egg in the fallopian tube. The sperm will penetrate the egg that leads to the formation of a fertilized egg. It's called a zygote. That single cell zygote has a complete set of chromosomes, half from the mother, half from the father, and then it begins to undergo rapid cell division.

(23:13): Okay? Rapid, rapid, rapid cell division forms a cluster of cells that are known as a blasto cyst. That blasto cyst then continues its journey down the fallopian tube towards the uterus, and that process can take six to 10 days. So it will be six to 10 days after fertilization that the blasto cyst will reach the uterus, and then once it reaches the uterus, it attaches to the lining of the uterus, and that process is called implantation. So fertilization is when they get together in the tube implantation is when it settles down in the lining of the uterus. Now, not all fertilized eggs will successfully implant an implantation. Failure can be a factor for people that have early pregnancy loss. Maybe the pregnancy didn't implant because the lining of the uterus wasn't fluffy enough or ready enough. That's where supplementing with progesterone may be helpful. Maybe the fertilized egg didn't implant because there are fibroids in the way, and so the spot where it tried to implant wasn't a good spot because the fibroid was there.

(24:37): So not all fertilized eggs will successfully implant. In fact, an ectopic pregnancy occurs when a fertilized egg not only does not implant, but it does not reach the uterus, so it doesn't make that trip down to the uterus, and instead, most often settles in the fallopian tube. You can't in certain circumstances, have ectopic pregnancies, and ectopic just means it's outside of the uterus. You can have ectopic pregnancies in the ovary and rare instances inside the abdomen, but most often ectopic pregnancies are going to be in the fallopian tubes. There's something about the tube that's sticky, or maybe there's a history of infection, and so it's not traveling down into the uterus like it should. Okay? So that is what an ectopic pregnancy is.

(25:32): Now, once the embryo or the blastos is implanted, it differentiates into two layers. The inner cell layer becomes the embryo, and the outer layer forms the placenta all, and that is the beginning of pregnancy. The developing embryo releases HCG human, that is the hormone that signals the corpus lium to continue producing progesterone during the early part of pregnancy until the placenta is big enough to take over. And then the progesterone helps to maintain the uterine lining and then just helps to support those early stages of pregnancy again until the placenta is big enough to take over that function. Okay?

(26:21): So isn't that a totally cool cycle of how all of that works together and it happens over and over and over again. Now, I want to end with a word about a couple of related things that are related, but it's kind of random. But these are things that come up in relation to the menstrual cycle and fertilization and implantation and ovaries that I just want to throw in here and talk about. So one is IUDs. I want to say a word about IUDs because sometimes you may hear people say that IUDs cause abortion. And I want to say where people get that from and why I believe it's wrong. So the way IUDs work is they work primarily by affecting sperm motility. They affect sperm viability like killing sperm, and they inhibit sperm function. They also thicken cervical mucus, make it more difficult for sperm to reach the egg, and it acts like kind of a barrier for sperm protection, that also the hormonal IUD makes it more difficult for sperms to move and reach the egg.

(27:29): And that hormone may also inhibit the L gastro in a hormonal IUD can also inhibit the ability of sperm to penetrate the egg. So those are the ways that the IUDs primarily work, but a secondary way that IUDs work is that they can prevent a fertilized egg from implanting. So if the sperm still reaches the egg and it is fertilized, that an IUD may prevent that fertilized egg from implanting. And because of that, some people consider that an abortion. Most OBGYNs do not consider that an abortion. An abortion is the interruption of an established pregnancy, and a fertilized egg is not an established pregnancy, it's just a fertilized egg. So it's not considered an abortion, but that is what some people mean when they say an IUD causes an abortion. Okay, the next thing I'm going to throw out there is anti-malaria and hormone. So anti-malaria and hormone is a protein that can be measured in your blood.

(28:39): It can help give you a estimate or a guess of how many follicles you have left in your ovaries, and that can help predict if you have any issues with fertility or how your ovaries are going to respond to fertility treatment. So anti-malaria, and hormone A MH is a protein that's produced by cells in ovarian follicles, and it's produced in relatively steady state levels. So it's like throughout the menstrual cycle. It doesn't go up and down. It stays pretty steady, so you can really measure it at any time during your menstrual cycle. And it's a blood test. It measures the concentration of a MH in your blood, and since it's produced by small growing follicles, the level of anti-malaria hormone can provide an estimate of the quantity of the follicles that are in your ovaries, and that's called ovarian reserve. So if you have lower levels of a MH, that might mean that you have a reduced ovarian reserve. You have a lower number of remaining eggs that are there for you to potentially get pregnant, whereas higher levels of A MH may suggest a greater ovarian reserve. So it's a piece of information that can help us understand how much ovarian reserve you have left. Now, it's important to note that it is valuable for assessing the quantity of eggs that are left, but not the quality. Okay? So A MH does not tell you about the quality of your eggs, only the quantity.

(30:32): And then the final thing I wanted to say is a note about getting a period while you're pregnant. Sometimes you see on TV shows or you see on the tiktoks or whatever, people are like, well, I was getting my period the whole time I was pregnant, and I want to clarify that by the medical definition of what a period is, that is not true. You can't get your period while pregnant. Your menstrual period by the medical definition is the shedding of the lining of the uterus that happens when you are not pregnant, and that is not possible to happen if you are pregnant. Now, you may be having bleeding while you're pregnant, and you may be having what you feel is regular bleeding for you, but it is not a menstrual period in the sense that it is the shedding of the lining of the uterus because you're not pregnant.

(31:38): Okay? If you're pregnant and you're having bleeding, it is not a period. All bleeding is not a period. All right? So that's just my little educational tip for the day. Okay? So just to recap, your menstrual cycle is a tightly coordinated cycle between the pituitary gland in your brain, your ovaries in your uterus. That results in the release of an egg during each menstrual cycle. It's very tightly coordinated, very orchestrated. In order to really produce just one egg for each cycle, you may notice changes in your menstrual cycle related to your libido, your mood, your energy, your skin, your appetite, your breast as you go through your menstrual cycle, that is totally normal. And tracking those changes may help you predict how things are in your life. Okay? As far as the menstrual cycle itself, it is divided into two phases. The first phase is the follicular phase that begins with the first day of your period.

(32:41): That is mostly about maturing that egg, getting that egg ready. Ovulation happens roughly in the midpoint of your cycle. Your fertile window is about five days. And then you go into the luteal phase, which is really just prepping for a potential pregnancy that is getting the uterus, the body ready for a potential pregnancy. Now, if implantation and fertilization occur, then you're pregnant. If not, then you start that cycle all over again. And as far as how long your cycle can be, cycles can be every 24 to 38 days and be considered normal. They can vary in length by seven to nine days. That is considered normal, and then they can last up to eight days. Okay, so there you have it. What surprised you about this episode? What did you learn that you didn't know before? I want to know. Shoot me a DM on Instagram and let me know what you learned from this show.

(33:43): Also, be sure to subscribe to the podcast, or I should say at Dr. Nicole Rankins on Instagram. If you didn't know. Also, subscribe to the podcast wherever you're listening to me right now. It helps the show to grow, and I appreciate you hitting that subscribe button. You also never, ever, ever miss an episode when you subscribe. Okay? And do check out the details of the birth preparation course, my online childbirth education class that gets you calm, confident, and empowered to have a beautiful birth. Check that out at drnicolerankins.com/enroll. So that's it for this episode. Do come on back next week and remember that you deserve a beautiful pregnancy and birth.