Understanding Your Uterus: What The Phases Of Your Period Mean : Short Wave Every month, 1.8 billion people menstruate globally. For those people, managing periods is essential for strong reproductive and emotional health, social wellbeing and bodily autonomy. But a lot of people haven't been educated about periods or the menstrual cycle since they were kids — if at all.

This episode, a period manual in four parts: How periods work, the different stages of the menstrual cycle, how to know when something's wrong, and whether to have a period in the first place.

The Period Talk (For Adults)

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EMILY KWONG, HOST:

You're listening to SHORT WAVE from NPR.

MARGARET CIRINO, BYLINE: Hey, Emily Kwong, SHORT WAVE co-host.

KWONG: Hey, Margaret Cirino, SHORT WAVE producer. What do you have for us?

CIRINO: OK, Emily. Today I'm going to give you the period talk but for adults, because I think, for a lot of us, the period talk kind of fell flat the first time around.

UNIDENTIFIED PERSON #1: I was so embarrassed to talk about it and, like, learn about it. I just felt so embarrassed.

UNIDENTIFIED PERSON #2: I distinctly remember her, like, taking a tampon and, like, putting it in a cup of water. And it just, like, (vocalizing).

UNIDENTIFIED PERSON #3: And it was the weirdest thing in the world.

MANDI TEMBO: Like, it was very clear that this is, like, a secret. And so don't go home and ask about this.

KWONG: I remember that feeling.

CIRINO: Yeah, and I think that's what a lot of my friends felt, as well, and also the period researchers that I've been talking to. They had these, like, really, really different but all really weird experiences learning about their periods.

KWONG: Which is odd, considering presumably half the planet gets it.

CIRINO: I know, yeah.

KWONG: And yet we still haven't figured out how to talk about it at all.

CIRINO: Yeah, and I think it's 'cause we learned in, like, all of these really strange ways. Like, I remember learning about it in the fifth grade when I was barely a person at that point. And they just, like, dragged me into a classroom with, like, all the other girls - the boys were in this separate room - sat us down for the period talk. And I swear I did not hear it mentioned in school after that.

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CIRINO: There's one researcher I talked to, Kristyn Brandi. She's an OB-GYN, abortion provider and family planning doctor. And she told me that she had tons of questions, even as a teen.

KRISTYN BRANDI: What is a period? Why does it happen? What if it doesn't happen in the normal way? And what is the normal way?

CIRINO: This was also Mandi Tembo's experience. She's pursuing a Ph.D. in menstrual health. And she realized that she could be the person in her friend group to really get this information out there.

TEMBO: I would always get questions from friends in the DM being, like, oh, what is that? Or, oh, I didn't know that anybody else felt like this.

CIRINO: Learning to manage your period, no matter what stage of life you're in, allows you to take control of your health, your emotional well-being, your social life, even your finances. So today on the show, it's the period talk but better, because the more we learn about our periods, the more control we have over our bodies. I'm Margaret Cirino.

KWONG: And I'm Emily Kwong. And you're listening to SHORT WAVE, the daily science podcast from NPR.

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CIRINO: OK, Emily. So I'm going to tell you a story in four parts. We're going to walk through how periods work, the different stages of the cycle, how to track them and how to know if something's wrong.

KWONG: This is the four-act play we didn't get in health class.

CIRINO: Yes. Yes, it is.

KWONG: This is the information we need. I'm going to step into the wings and let you take center stage. Margaret Cirino, good luck.

CIRINO: I'll miss you, EK. But let's get into it. First up, what even is a period? It's a shedding of the uterine lining through the cervix and out the vagina. And it happens because the body's preparing for the possibility of a pregnancy. So the cycle begins with the day that you first start bleeding - you know, when you're, quote-unquote, "on your period." So that shedding of the uterine lining usually happens once a month. You know, it lasts between three and seven days, but that changes. And...

TEMBO: Our bodies are not clocks. So this idea that every cycle is 28 days - sometimes things interfere, and there are fluctuations in our hormones and people are very different.

CIRINO: There's one hormone in particular that signals your body to start bleeding. It's called progesterone. It's how your body knows to shed the uterine lining it's built up when progesterone levels plummet.

BRANDI: If you are pregnant, progesterone levels will skyrocket. And so that will help your body be ready to continue a pregnancy. But if you're not pregnant, the progesterone levels will drop and, once it drops below a certain level, will signal to the body that the lining is no longer needed because you're not pregnant. And so that will start the process of it shedding.

CIRINO: So a lot of people might feel much lower energy.

TEMBO: Your body's doing work at the minute and shedding a lot of blood. Some mood swings. You're less social. You just want to rest.

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CIRINO: Step 2 of the menstrual cycle - 'cause, you know, the bleeding is actually only the first part. After you've shed your whole uterine lining, your body gets ready to release another egg. And this is called the follicular step. That's typically around Day 6 of your cycle. And that's when the body's actually growing that egg. Mandi says the follicles are those little sacs in the ovaries that contain all the immature eggs.

TEMBO: So you have all these hormones in your body that are stimulating the growing of the follicles.

CIRINO: Like, Kristyn says, follicle-stimulating hormone, or FSH.

BRANDI: To signal to the ovary to get an egg ready so that it can be released by the time of ovulation. And FSH is also the signal that the brain sends to the ovary to make estrogen.

CIRINO: Right.

BRANDI: The estrogen works as a biochemical to signal to that part of the uterus, which usually has a very base layer, to start producing cells. And it also helps bring blood vessels into that area to help supply those newly built cells to keep building more and more layers, to eventually create this very big lining.

CIRINO: Time for Step 3 - ovulation. That's after the follicular step, and that's when the egg itself is released. That's typically around Day 14. So estrogen peaks in the days leading up to ovulation, and that signals the brain to send out a new hormone called LH.

BRANDI: Or luteinizing hormone. And that LH, when it surges, when it spikes, that's the signal that the ovary needs to release an egg.

CIRINO: This is also when the body is most fertile. And Kristyn says this period of fertility can actually be pretty long.

BRANDI: So typically, the fertile window can be anywhere between two to three days before when the egg is released to two to three days after the egg is released. It's a pretty big window - about six days or so. The reason for that is that sperm actually can hang out in that area for about 72 hours before they die.

CIRINO: Next up, the luteal step, which is about the last 14 days of your cycle. It's named after something called the corpus luteum. That's a group of cells that forms in the ovaries after the egg has left to help the uterus become a healthy place for a fetus to grow.

BRANDI: And so the corpus luteum, its main job after it releases the egg is to make a hormone called progesterone. And that helps both get the lining ready for a potentially fertilized egg to be implanted, and it also just gives your body signals that, like, an egg is released, to get your body ready - that if it's pregnant, that it'll continue to make progesterone, which is the main hormone that your body needs to stay pregnant.

CIRINO: The body can be really sensitive to these changing hormone levels, especially around the luteal step, you know, if a person hasn't become pregnant, because that means hormones are plummeting.

BRANDI: And the reason for that typically is that at this point, after the rise in progesterone, the progesterone will drop and all the other hormones we talked about earlier...

CIRINO: Like estrogen, FSH and LH.

BRANDI: ...All of those hormones will drop to its lowest level. And some people are really sensitive to that change, so much so that it can cause things like mood swings, difficulty sleeping, GI symptoms, headaches, difficulty concentrating.

CIRINO: This is called PMS, or premenstrual syndrome.

BRANDI: And they usually stop once a period actually starts because, at that point, the cycle is kind of restarting again, and the hormone levels are starting to go up.

CIRINO: And so after the luteal step, we go right back to the beginning, the menstrual step, when you're on your period.

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CIRINO: So to recap, the menstrual cycle begins with the first day of your period, which is your body shedding its uterine lining. Then after the menstrual step is the follicular step. A hormone called FSH lets your ovaries know to start prepping an egg and producing estrogen. After the follicular step comes ovulation, when a hormone called LH causes your body to release the egg. And lastly, the luteal step. The body produces progesterone in case of pregnancy, though if there isn't a pregnancy, the hormones plummet, triggering your period to start all over again.

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CIRINO: So what do we do with all this info? Enter period tracking, even with just a pen and paper, like me. Talking with Mandi and Kristyn, it's clear that knowing how your period works isn't enough. It's also important to track your individual cycle so you and your doctor can manage it throughout the month.

BRANDI: If you're having pain a couple of days before your period, maybe you can start taking medication to help with the pain a little bit earlier than that.

CIRINO: Tracking can also help you notice when something's wrong. Mandi says if your pain is stopping you from going about your day, see a doctor because it might be a sign of a common disorder.

TEMBO: There are quite a few conditions that can cause really painful periods, the common ones being fibroids, which are growths in the uterus. And that can cause pain and discomfort. That could also prolong bleeding. So if you usually bleed for four or five days and now you're bleeding for 12 to 14 days, that's an indication that something might be wrong.

CIRINO: This is all a lot to keep tabs on. And it makes me wonder, do you even need a period?

BRANDI: If you're not trying to get pregnant and you don't like having a period, it's not something that is necessary for your health or well-being.

CIRINO: Which is why Kristyn says you could choose to stop it completely with medication.

BRANDI: So, for example, if you're taking the pills, you would skip the placebo pills and go straight into your next pack so that you're always at the same level of hormones.

CIRINO: Methods like a hormonal IUD or an implant can sometimes keep you from having a period for years, she says.

BRANDI: There are some people that having a period is really problematic for them, and so it may be preferable to avoid having a period. There's other people on the transgender and gender nonbinary spectrum where having a period may be dysphoric and may be incongruent with their gender identity. And so it may be really important for someone to use medications to stop having a period so they feel more like what their natural body should be. And then there's other people, potentially with developmental delays, that have periods that may be difficult to manage and may be uncomfortable for them. And all of those reasons are valid and great, and we should try to help support people if that's what they want.

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CIRINO: This episode was produced by me, Margaret Cirino. It was edited by Gisele Grayson and Rebecca Ramirez. Brit Hanson checks the facts, and the audio engineer was Alex Drewenskus. Brendan Crump is our podcast coordinator. Our senior director of programming is Beth Donovan, and the senior vice president of programming is Anya Grundmann. I'm Margaret Cirino. Thanks for listening to SHORT WAVE from NPR.

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CIRINO: So do periods actually sync up when, you know, you spend a lot of time with someone? Like, will me and my roommates sync up?

TEMBO: Yeah, so I think that's obviously something that we've learned from TV a lot. That is not true. Let's just put it that way. Yes.

CIRINO: Yeah.

TEMBO: That's not a thing. Yeah.

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