If you spend enough time on the wellness side of TikTok, and the algorithm has identified you as someone who probably gets a period, you'll eventually take a virtual seat in front of a person narrating her experience tracking her period with help from the Oura ring, as the smart ring shimmers inconspicuously on the speaker's finger. 

But don't be fooled by the subtlety. This smart ring is smack-dab between two wellness trends: a heightened interest in going off hormonal birth control to take inventory of the body's natural menstrual cycle, and using technology to gain more insight into it.

People are prescribed hormonal contraception for reasons other than protection against unplanned pregnancies. It can be an effective treatment for a variety of health conditions, including polycystic ovary syndrome, endometriosis, severe acne and premenstrual dysphoric disorder, which may all be eased when the body's natural hormonal fluctuations are temporarily leveled. (Despite some misinformation swirling online, research shows that hormonal birth control doesn't affect future fertility, and in certain cases may actually help it.)

Combined birth control pills pause ovulation, which also temporarily masks what the US Centers for Disease Control and Prevention calls a "valuable marker for overall health," a pattern that can tell you how other parts of your body are working. In a world that's increasingly interested in analyzing how every angle of our body is working, some people who've been on birth control pills much of their life are interested in what their "real" menstrual cycle will show them. Those who've already seen it want to take a closer look.

Dr. Shaalini Ramanadhan, a family planning specialist and assistant professor in the department of obstetrics and gynecology at Oregon Health and Science University, said there are challenges someone will face if they want to track their fertility accurately as the process requires consistent monitoring of different body signals. 

It's even more challenging for people who haven't had a regular cycle and don't have a sense of where they are in their menstrual cycle (like the follicular phase which leads up to ovulation, or the luteal phase before menstruation begins). This includes people who've just recently come off hormonal birth control -- the American College of Obstetricians and Gynecologists specifically names this group as needing more guidance to accurately track fertility.

"I appreciate that people want to understand their bodies more," Ramanadhan acknowledged. "That they're curious about their body and want to see what their body is capable of."

"We also enjoy data now," she added. "There's something satisfying about seeing your own body do its normal process." 

Enter: Wearables. Then, more specifically, enter the Oura ring, a popular sleep tracker that can deliver basal body temperature readings throughout the night, all in a jewelry-esque package more marketable to women. This all made Oura a natural partner for Natural Cycles, the first app cleared by the US Food and Drug Administration to call itself a birth control app. Oura ring offers its own Cycle Insights, but this isn't meant for contraception and is not as comprehensive as the cleared app.

Natural Cycles pulls basal body temperature data from the Oura ring to train its algorithm to give someone an estimate of their fertile vs. infertile windows; if you're using it as birth control, you need to abstain from unprotected sex during fertile or "red" days. Temperature data from the Apple Watch may also be pulled into Natural Cycle's algorithm, but you need to wear the watch to bed, which may be less comfortable for some.

More people are using Natural Cycles, and they're taking their wearables with them. According to information from Elina Berglund Scherwitzl, Natural Cycles' co-founder and CEO, the app saw a 50% year-over-year growth in new users. Most users (60%) already have an Oura ring or Apple Watch. 

But in addition to Natural Cycles' algorithm being highly specific on what can affect basal body temperature data (common experiences like sleeping poorly, drinking alcohol the day before, being sick and wearing your ring or watch incorrectly all invalidate Natural Cycles' data), temperature shifts related to ovulation can only tell you after you've ovulated, which means Natural Cycles' algorithm, and temperature-tracking in general, is based on past trends. This is notable because even in people with very regular cycles, ovulation varies a little cycle to cycle.

Natural Cycles says its fertility awareness algorithm is as effective as birth control pills with typical use. In general, fertility awareness methods are more effective if you use more than one. For example, tracking cervical mucus can be beneficial because it should appear before ovulation when pregnancy starts to become possible, but it's usually less easy for people to gauge than basal body temperature, Ramanadhan said, and that's why people tend to do both. You may also test for a surge of hormones ahead of ovulation with LH strips. 

If this is starting to sound like the work of a scientist, you've got it. That's the kind of work you need to be down for if you're interested in accurate cycle tracking. Adding new, improved technologies to the equation may hopefully take some of the leg work out of discerning our bodies' patterns, but they also come with new risks, like the algorithm getting it wrong and fears around more companies having access to personal reproductive data. Concerns related to data security and unintended pregnancy may be heightened in many parts of the US, where states have continued to restrict or ban abortion following the overturning of Roe v. Wade in 2022. 

The menstrual cycle as a 'vital sign' and why tech companies are after it

The menstrual cycle has long been recognized in the medical community as a big window into someone's overall health. 

This is because your cycle relies on multiple systems, such as communication between the brain and the ovaries, a balance of hormones and adequate calorie and nutrient intake. Stressful life events, illnesses and big health events like pregnancy and perimenopause are expected to cause irregular or absent cycles here or there, but regular and predictable menstrual cycles are a good sign someone's body is getting basic needs met. 

Consistently irregular cycles, and those that are painful, often signal underlying health conditions or something that needs to be addressed. Newer research suggests they may be a sign of future health risks, too: Studies have linked irregular periods to increased risk of cardiovascular disease. 

Big tech companies, which continue to stack their wearables with health metrics to win the dollars of people who want more holistic views of themselves, know this. Apple, for example, has dedicated a years-long research effort specifically to the menstrual cycle, using data it collects from the Health app and its Apple Watch from people who choose to share it. Preliminary results from Apple, conducted with the Harvard T.H. Chan School of Public Health and the National Institute of Environmental Health Sciences, connect irregular periods to PCOS, as well as an increased risk of health conditions like diabetes and high blood pressure.

One increasingly vocal group who say they were never given access to this detailed view of their menstrual cycle, however, are younger people who say they were automatically prescribed birth control without getting a full run-down on the reasons, or options on how to manage without it.

Dr. Navya Mysore, a primary care physician and women's health expert, says she's had patients who've taken birth control since they were teenagers, after they somehow "found themselves in a gynecologist's office and were prescribed birth control." 

She stressed the role birth control can play in managing certain conditions, such as PCOS, as well as its role in contraception (controlling pregnancies and births). Anyone wanting to come off it should talk with their doctor, she said, especially if they were put on it to treat a health condition. 

But, like Ramanadhan, she sees an "empowerment" in a younger generation looking for information on their own bodies.

"I will never tell a patient to not explore that," Mysore said. "I think it's important when you are making that decision that you're doing it responsibly." 

One thing to take into account is how prone health information is to being inaccurate online, simply by its nature of "little sound bites," Ramanadhan said. 

"If people are fed these quick tips and tricks for something that is really deeply individual and extremely personal -- all of that is really depleting and confusing, I think," she said.

Another thing to consider before you add Oura, Natural Cycles or any other wearable or app to your health routine is that ultimately, it's a company that wants to sell you something, usually at a high cost. Oura rings start at $299 and require a $6 monthly subscription. Natural Cycles costs $120 annually for new users, or $17 monthly. If you buy an Oura ring through Natural Cycles, it's $40 off. 

How Oura ring and wearables can (and can't) help track ovulation

Ovulation, the release of the egg from the ovary, is the main event of the menstrual cycle, and it occurs near the end of a roughly six-day fertile window about two weeks before menstruation begins. While an egg can only survive for a short period of time after it's ovulated, sperm can survive up to five days, which is why scientists have estimated the fertile window lasts about a week. For people tracking fertility either to achieve pregnancy or prevent it, it's essential to identify this fertile window in which conception is possible. 

Fortunately, there are a few key biomarkers and signs you can look out for. 

Rising levels of estrogen open up the fertile window by changing the consistency and amount of cervical mucus. This creates an environment that makes it easier for sperm to survive long enough to fertilize an egg. 

Close to or during ovulation, some people report cramping, bloating, breast tenderness and more, though keep in mind these would typically begin after the fertile window has already opened. Mood changes and higher energy levels can also be more noticeable in the middle of a cycle. 

One thing that marks ovulation once it's happened -- and which can be used as part of a pattern to predict what will happen next month -- is a slight rise in basal body temperature, a more precise reading than traditional temperature. This is the main data that feeds the Natural Cycles algorithm to estimate ovulation, though it also takes LH strip test results. Because Oura ring and some Apple Watch models have temperature sensors that can take this metric, Natural Cycles can use the data for its algorithm. The app says it has plans to add more wearables.

I've tried cycle tracking using Natural Cycles with the thermometer the company gives you. I've always had very regular cycles, so I figured I would be a good candidate, and I'm interested in how technology is moving into a space that seems to lock in a lot of health information. I wanted to see what more I could find.

But I stopped Natural Cycles after a couple of months because the temperature-taking requirements with the basal thermometer are extremely finicky -- you need to take your temperature first thing in the morning, before even taking a sip of water, getting out of bed or barely moving at all -- and outside factors can affect readings, like how much sleep you got, whether you drank alcohol the day before and more. 

My poor sleeping patterns and snooze-button habit, in particular, became an issue, so the work out-valued the worth and I ditched Natural Cycles before the algorithm had enough data to reasonably reflect my own trends. But because my experience was limited to the thermometer, I've been curious how Oura ring and future models could help people take some of the pain out of daily tracking.

What about the Evie Ring?

The Evie ring, a new challenge in the smart ring market, is positioning itself as a health tracker specifically for women with a more holistic view of data and a ring size that fits fingers that may change size with hormonal fluctuations. Other Evie features that may have Oura beat include the fact that it's more affordable ($269), it doesn't require a monthly subscription (like Oura's extra $6 a month) and it may even look a little more like regular jewelry, thanks to its svelte design.

Crucially, though, Evie doesn't have the ability to track basal body temperature, meaning it can't currently pair with Natural Cycles or use basal body temperature to help narrow fertile windows. While it's too soon to say whether the ring will ever pair with Natural Cycles, Evie does have plans to move into temperature tracking.  

Stacy Salvi, vice president of strategy at Movano Health, told CNET in an email that the company will "begin working on that integration this summer." Salvi added that Evie integrates menstrual cycle insights based on user logs with mood, energy, sleep and heart health, which will help people interpret their own patterns.

Combining Evie's entrance into the market with the anticipation around Samsung's new Galaxy Ring on the horizon, more wearables challenging Oura's status quo as a smartring could result in more refined health metrics -- and better data for those wanting to improve the health of their menstrual cycle.

Read more: Galaxy Ring: My Hands-On Experience With Samsung's Chic Wearable

Beyond the apps and algorithms

Cait Molony, a fertility awareness instructor based in Toronto, uses Natural Cycles and has an Oura ring. On TikTok, she advises against people using only temperature-based tracking as birth control, citing a high number of people in her comments who say they got pregnant doing just that. 

Expanding on one of the videos she's posted about technology-based fertility tracking, she stressed these technologies are just that -- technology. And sometimes, the tech gets it wrong.

"The problem with Natural Cycles is that it's an algorithm, and one of the first rules you'll learn when you're learning fertility awareness is that you can't actually rely on previous cycles to determine your fertility status in this current cycle," Molony said, emphasizing the importance of additional awareness methods, like tracking cervical mucus. 

Molony stressed that fertility tracking is "not for everyone" and "not something you can do haphazardly." She pushed back on the narrative that everyone interested in the benefits of cycle tracking is anti-birth control. She's not; she says many people are not good candidates for FAM. But she says she has a "classic story" of being prescribed birth control as a teenager, before she fully understood her body. When she decided to come off, she struggled to understand where she was in her menstrual cycle, which is why she wants to help people get to the bottom of theirs.

Mysore and Ramanadhan reiterated the extra caution someone needs to take if cycle tracking is their main form of birth control. They also stressed that there's room to grow in terms of patient-doctor transparency when a person is prescribed birth control. 

"I really do think that we have done a very poor job in terms of educating our population," Mysore said. "I think they are asking, seeking answers more than we were before, and I'm happy to see that."