When Might You Ovulate?
See when your fertile window may be approaching, so you can feel more confident about when to try.
Fibra smart underwear automatically tracks 5 ovulation signals to help you conceive faster and better understand your fertile window—non-invasively, just by wearing it.
Get FibraBuilt into soft, breathable, cotton underwear, Fibra tracks your body’s changing signals and turns them into personalized ovulation insights.
around ovulati0n
Becomes less acidic
Volume increases
Rises
Increases
Higher
Absolutely! Fibra is machine washable, dryer safe, and reusable, just like your everyday underwear. Simply detach the electronic unit before washing, and you're good to go! Make sure to follow the care instructions.
Your safety and comfort come first. Fibra is designed for non-invasive monitoring, with no needles or internal devices. Our smart underwear has undergone biocompatibility testing at a specialized laboratory in Germany, and our development process follows applicable ISO and IEC safety standards. Read more here.
We recommend taking a break from Fibra during your period. Simply resume wearing it once your period ends, and Fibra can continue tracking your body's changing signals throughout the rest of your cycle.
You can get started with just two smart underwear! For effortless daily wear, we recommend having at least three, one to wear, one in the wash, and one ready for tomorrow.
Fibra's sensors are already built into the fabric, so there's nothing to attach or adjust! A slim, flexible electronic unit containing the battery and Bluetooth module simply snaps into the waistband. Just pop it off before washing and snap it back on when you're ready to wear Fibra again.
Have a question?
Book a 1:1 meeting with Parnian or send us an email. We're here to help.
Parnian Majd Founder & CEO, Fibra
Your cycle changes. Fibra helps you understand it.
See when your fertile window may be approaching, so you can feel more confident about when to try.
Discover how sleep, activity, and other factors may relate to your ovulation timing and cycle patterns.
Your cycle doesn’t always follow a calendar. Fibra uses your changing body signals to update your personalized predictions.
Understand the signals leading up to ovulation, recognize your unique patterns, and feel more confident about when to try.
Biomarker data points
Women in our community
Minutes of real-world wear
Designed with privacy, safety and comfort in mind.
Built for fertility signals, not just prediction.
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| Built specifically for fertility & reproductive cycles | ✓ | ✓ | ✓ | × | ✓ | × |
| Uses multiple reproductive + fertility signals | ✓ | × | × | × | × | × |
| Tracks automatically | ✓ | × | × | × | ✓ | ✓ |
| Tracks continuously | ✓ | × | × | × | ✓ | ✓ |
| Cycle and fertility insights update as new body data comes in | ✓ | × | × | × | ✓ | × |
| Non-invasive | ✓ | ✓ | ✓ | ✓ | × | ✓ |
| No testing, measuring, or manual logging | ✓ | × | × | × | × | ✓ |
| Built into something you already wear | ✓ | × | × | × | × | × |
Choose the Fibra that best fits your routine.
First 50 units only
Only pay for the electronic unit and get 2 smart underwears for free.
Everything you need to start.
Wear one. Wash one.
Fibra for more of your week.
One for every day.
Maria, 30
“Every fertility tracking tells me the same thing. Excited for Fibra’s personalized insights.”
Nina, 31
“I can finally know what’s going on with my cycle! Felt heard in this journey trying to conceive.”
Jess, 28
“I like being able to look back at my data and actually understand the patterns I’m seeing.”
Rose, 27
“The biggest difference for me is having more context around what’s happening in my cycle instead of relying on predictions.”
Camila, 29
“I rely less on calendar predictions now. Tracking fertility feels much less overwhelming.”
Tammy, 27
“Fibra makes tracking ovulation feel so much simpler. And it’s non-invasive!”
Amanda, 33
“Fibra makes fertility tracking feel more personalized. No more relying on averages.”
Kelsy, 33
“Simple and easy to use. It makes TTC tracking feel much more manageable.”
Charlotte, 31
“I wanted to understand my cycle better as we started planning for a baby. Fibra made tracking feel like a natural part of my routine, rather than another thing on my to-do list.”
Emma, 34
“Trying to conceive can feel overwhelming. Having my cycle information in one place with Fibra helped me feel more informed and a little more grounded along the way.”
Yusra, 29
“Didn’t think I could actually know my fertile window as someone who has irregular cycles.”
Sophia, 25
“Super comfortable and soft. Understanding my cycle doesn’t feel like a burden anymore!”
Frequently Asked Questions
How can Fibra help me understand when I’m fertile?
Fibra continuously follows five reproductive and physiological signals during wear—vaginal pH, discharge patterns, skin temperature, heart rate, and HRV—to help you understand when you may be ovulating and when your fertile window may be.
Instead of relying only on calendar dates, temperature, or a single moment of data, Fibra brings multiple signals together to build a more personalized picture of what your body is doing this cycle.
As new data comes in, your estimated ovulation timing and fertile-window insights can update if your timing shifts—even when your cycle doesn’t follow the expected schedule.
Just wear it. Less tracking. Less guessing about when you may be fertile.
Your cycle changes. Fibra updates with it.
Can Fibra work if I have PCOS or my cycle changes every month?
es. Fibra is built for cycles that change, including irregular or unpredictable cycles.
When your cycle length varies from month to month, calendar dates alone may not reflect what your body is doing this cycle. Instead of assuming your ovulation or period will happen on the same schedule every month, Fibra continuously follows multiple reproductive and physiological signals during wear to build a more personalized picture of your changing cycle.
You don’t need to know how long this cycle will be in advance for Fibra to follow how your signals are changing. As new body data comes in, your cycle, estimated ovulation, and fertile-window insights can update as your timing changes—helping you better understand when you may be fertile without relying on your cycle following the expected schedule.
Your cycle doesn’t have to be predictable for Fibra to follow it.
Fibra helps you track and understand your cycle; it does not diagnose or treat PCOS.
How accurate is Fibra at tracking my cycle and estimated fertile timing?
Fibra doesn’t rely on a calendar prediction or a single body signal to understand your fertility.
It continuously follows five reproductive and physiological signals during wear—vaginal pH, discharge patterns, skin temperature, heart rate, and HRV—and looks at how they change together over time and throughout your cycle.
That matters because individual signals can be influenced by everyday factors. Alcohol, poor sleep, illness, stress, or changes in routine can affect signals such as temperature, heart rate, or HRV. Rather than relying on temperature alone, Fibra considers changes in one signal alongside the rest of your body data.
Fibra also includes reproductive-specific signals such as vaginal pH and discharge patterns, adding information that temperature-only tracking doesn’t capture.
And your fertility timing isn’t treated as fixed. As new body data comes in, your estimated ovulation timing and fertile-window insights can update as your cycle changes, creating a more personalized picture of what your body is doing this cycle.
Multiple signals. Over time. Personalized to your current cycle. A more complete picture of your fertility.
How is Fibra different from fertility apps and period trackers?
Fertility apps and period trackers can be useful—but Fibra gives you a different layer of information: body signals collected automatically during wear.
Apps typically build predictions and insights from information such as your cycle history, dates and symptoms you log, test results, or connected-device data, depending on the app. Fibra is the wearable collecting the data itself—continuously following five reproductive and physiological signals: vaginal pH, discharge patterns, skin temperature, heart rate, and HRV.
That includes reproductive-specific signals like vaginal pH and discharge patterns, giving Fibra information beyond the temperature and general physiological signals commonly available from wearables. And because Fibra follows these signals throughout wear, it can capture how they change over time—not just a single measurement or manually logged moment.
That distinction matters when your cycle changes. Rather than relying only on what happened in previous cycles or information you manually enter, Fibra collects new body data during wear, so your estimated ovulation timing and fertile-window insights can update as your cycle changes.
And because Fibra collects its sensor data automatically, you don’t have to manually log those measurements yourself.
Go beyond calendar predictions with reproductive and physiological signals from what your body is doing this cycle.
Why does Fibra track five signals instead of temperature alone?
Ovulation tests, BBT tracking, and fertility wearables can all provide useful information—but they give you different pieces of the fertility picture. Fibra brings multiple signals together in one system.
Ovulation tests measure specific hormones at the time you test. BBT tracking focuses on temperature patterns. Fertility wearables vary by product and measure different signals depending on their sensing approach.
Fibra continuously follows five reproductive and physiological signals during wear—vaginal pH, discharge patterns, skin temperature, heart rate, and HRV. That includes reproductive-specific signals like vaginal pH and discharge patterns, rather than relying on temperature or a single type of signal alone.
This matters because a single signal doesn’t always tell the whole story. Temperature, for example, can be influenced by sleep, illness, alcohol, and changes in routine. Fibra considers temperature alongside multiple other signals to build a more complete picture of what your body may be doing this cycle.
Fibra also follows these signals throughout wear and over time, rather than relying only on individual testing or measurement moments. As new body data comes in, your estimated ovulation timing and fertile-window insights can update as your cycle changes.
And there’s less to remember: no manually taking Fibra’s sensor measurements or logging them yourself. Just wear Fibra and let it collect the signals during wear.
Fibra is also non-invasive—there’s no device to insert—and you can continue using other fertility tools alongside it if you choose.
Multiple signals. More than one moment of data. Less manual tracking. One system built to follow your changing cycle.
How is Fibra different from ovulation tests, BBT tracking, and fertility wearables?
Ovulation tests, BBT tracking, and fertility wearables can all provide useful information—but they give you different pieces of the fertility picture. Fibra brings multiple reproductive and physiological signals together in one system.
Ovulation tests measure fertility hormones at the specific times you test. BBT tracking follows temperature patterns. Fertility wearables vary by product and measure different signals depending on where and how they are worn.
Fibra takes a different approach. During wear, it continuously follows five reproductive and physiological signals—vaginal pH, discharge patterns, skin temperature, heart rate, and HRV. That includes reproductive-specific signals like vaginal pH and discharge patterns, rather than relying on temperature or a single type of signal alone.
This matters because one signal doesn’t always tell the whole story. Temperature, for example, can be influenced by factors such as sleep, illness, alcohol, stress, and changes in routine. Rather than relying on temperature alone, Fibra looks at it alongside other reproductive and physiological signals to build a more complete picture of what your body may be doing this cycle.
Fibra also follows these signals throughout wear and over time, rather than relying only on individual testing or measurement moments. This gives Fibra ongoing information about how your signals are changing as your cycle unfolds.
As new body data comes in, your estimated ovulation timing and fertile-window insights can update as your cycle changes—particularly useful when your ovulation doesn’t happen when you expected it to.
And there’s less for you to do. You don’t have to manually take Fibra’s five sensor measurements or log them yourself. Just wear Fibra, and it collects the signals automatically during wear. Fibra is also non-invasive, with no device to insert.
Multiple signals. More than one moment of data. Less manual tracking. One system built to follow your changing cycle.
Can I use Fibra alongside Flo, Clue, Natural Cycles, Inito, or other fertility tools?
Yes. You can use Fibra alongside the fertility apps, tests, and wearables you already use. You don’t have to replace your current tools to start using Fibra.
Different fertility tools can give you different types of information. Apps such as Flo and Clue use information such as cycle history and data you track to provide cycle and fertility predictions and insights. Natural Cycles uses temperature, period data, and optional LH data to calculate fertility status, while Inito measures four urinary fertility hormones—E3G, LH, PdG, and FSH.
Fibra adds a different layer: five reproductive and physiological signals collected automatically during wear—vaginal pH, discharge patterns, skin temperature, heart rate, and HRV. This includes reproductive-specific signals such as vaginal pH and discharge patterns, giving you another way to understand what your body may be doing throughout your current cycle.
So if you already log your cycle in Flo or Clue, track temperature with Natural Cycles, or test hormones with Inito, you can continue doing that while using Fibra. Fibra follows its own signals during wear and turns them into your Fibra cycle and fertility insights.
As new Fibra data comes in, your estimated ovulation timing and fertile-window insights can update as your cycle changes, without requiring you to manually take or enter Fibra’s sensor measurements.
Keep the fertility tools you find useful. Fibra adds continuous, multi-signal body data from something you already wear.
How often do I need to wear Fibra?
For the best experience, we recommend wearing Fibra everyday/every night throughout your cycle—not only on the days you expect to be fertile.
Fibra is designed to understand how your reproductive and physiological signals change over time. During wear, it follows vaginal pH, discharge patterns, skin temperature, heart rate, and HRV. Wearing Fibra consistently gives it a more complete picture of how those signals are changing across your cycle.
That’s particularly useful when you’re trying to conceive because you may not know your fertile days in advance—especially if your cycle timing changes. Rather than waiting until the day you think you’re ovulating, Fibra can follow how your signals change as your cycle unfolds.
You don’t need to wear Fibra 24/7 and if you miss 2,3 days in between the accuracy is still 95%+. In general, more consistent wear means a more complete record of your cycle.
You don’t have to plan your life around fertility tracking. Fibra is designed to fit fertility tracking into something you’re already doing: getting dressed.
Is Fibra comfortable, washable, and safe to wear regularly?
Yes. Fibra is designed for regular, everyday wear—with comfort, washability, and body contact considered throughout its development.
Comfort: Fibra is designed to be worn like regular underwear, with the sensing technology integrated directly into the fabric and a small detachable electronic unit. Across real-world testing, Fibra has accumulated 500,000+ minutes of wear, helping us refine the product for everyday use.
Washability: Fibra is machine washable. Simply remove the detachable electronic unit before washing, then place the underwear in your washing machine at a normal temperature on a normal cycle. Fibra can also be placed in the dryer at a normal temperature for up to 60 minutes. Once it’s clean and dry, reattach the electronic unit and wear it again.
Safety: Fibra is non-invasive and designed for regular external wear. The fabric-based sensors have undergone cytotoxicity testing based on ISO 10993 and passed the cytotoxicity test, helping evaluate the biocompatibility of the sensor materials that come into contact with the body.
Unlike an inserted fertility device, there’s nothing to insert and no daily test to take. The sensing technology is built into something you’re already wearing.
Wear it. Remove the electronics. Wash it. Wear it again. Fibra is designed to make reproductive tracking fit into everyday life.
When will I receive my Fibra, and where do you ship?
Fibra is available to order now, and your order is expected to ship within 2–3 weeks.
We currently offer free standard shipping to Canada and the United States.
What if I don’t ovulate every cycle?
Fibra doesn’t assume that everyone ovulates on the same cycle day—or that every cycle will follow the same pattern.
With PCOS and irregular cycles, ovulation can happen later than expected, and some cycles may not follow the pattern you anticipated.
Rather than assigning ovulation to a fixed calendar day and assuming your body will follow it, Fibra continues following your reproductive and physiological signals as your current cycle unfolds.
So if your cycle keeps going beyond the timing you expected, Fibra can continue collecting information about how your patterns are changing instead of simply treating your cycle as “late.”
Fibra does not clinically confirm whether ovulation occurred or diagnose anovulation. If determining whether you are ovulating is medically important, a healthcare professional can recommend appropriate clinical or hormone testing.
Fibra follows your changing cycle instead of assuming it will follow a textbook one.
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