What may be coming next?
See when your period, fertile window or other changes may be approaching.
Fibra smart underwear automatically tracks 5 reproductive signals to help you understand your unique cycle patterns and recognize changes, even when your periods are unpredictable. Just wear it.
Get FibraBuilt into soft, breathable, cotton underwear, Fibra tracks your body’s changing signals and turns them into personalized ovulation insights.
your unique cycle patterns
Changes in acidity
Shifts in fluid patterns
Helps distinguish cycle phases
Changes between cycle phases
Shifts in recovery patterns
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.
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 period, fertile window or other changes may be approaching.
See how things like sleep, activity and other tracked factors may relate to changes in your cycle and body over time.
See where you may be in your cycle, how it’s progressing, and what your changing body signals reveal, even when your cycles are unpredictable.
Understand your unique cycle patterns, recognize what repeats, and spot changes—even when your periods are unpredictable.
Biomarker data points
Women in our community
Minutes of real-world wear
Designed with privacy, safety and comfort in mind.
A more complete and continuous way to understand your cycle with PCOS.
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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 everything means! Thank you for what you’re doing for women’s health!”
Jess, 28
“Losing weight seemed impossible for me until I started paying attention to my reproductive health.”
Rose, 27
“As a physician, women deserve continuous reproductive health monitoring. Fibra gives women what they need!”
Camila, 29
“At first I wasn’t sure if I should order now or wait but the fact that I get lifetime access to the app did it for me! <3″
Tammy, 27
“I used to constantly wonder if the changes I noticed were normal. Fibra is giving women clarity!”
Amanda, 33
“My body felt completely different postpartum. I love that Fibra s giving women so much clarity.”
Mitchel, 29
“If this helps me catch something earlier…it’s worth every dollar. Amazing to see product like this!!”
Charlotte, 31
“Got diagnosed with PCOS when I was 15. I’ve waited my whole life for something like this.”
Emma, 34
“As someone going through menopause this will change my life completely!”
Yusra, 29
“I love that Fibra is giving women a new way to understand their reproductive health.”
Sophia, 25
“If this actually works the way it says…this changes women’s healthcare”
Frequently Asked Questions
How can Fibra help me understand my cycle if I have PCOS or irregular periods?
Fibra is designed to help you understand your cycle even when it doesn’t follow the same schedule every month.
With PCOS or irregular periods, what happened last cycle may not tell you exactly what your body is doing this cycle. That can make it difficult to know where you are in your cycle or what may be coming next.
Instead of relying only on calendar dates, Fibra continuously follows five reproductive and physiological signals during wear—vaginal pH, discharge patterns, skin temperature, heart rate, and HRV—to build a more personalized picture of your changing cycle.
As new body data comes in, your cycle insights can update if your timing shifts, helping you better understand where you may be in your cycle and what may be coming next.
The goal isn’t simply to give you more data. It’s to help you spend less time guessing, experience fewer surprises, and better understand your changing cycle so you can plan your life around it.
Your cycle may be unpredictable. Understanding it doesn’t have to be.
Fibra provides reproductive-wellness insights and does not diagnose or treat PCOS.
Can Fibra work if my cycle length changes every month or my cycles are very long?
Yes. Fibra is built for cycles that change—including long, irregular, and unpredictable cycles.
You don’t need to know in advance whether this cycle will be 30, 40, 50, or more days long for Fibra to follow how your signals are changing.
Instead of assuming your current cycle will follow the same timeline as your previous ones, Fibra continues collecting reproductive and physiological data during your current cycle.
That matters because if your timing changes, Fibra has new information from what your body is doing now. Relevant cycle insights can update rather than remaining tied to the timing originally expected.
So you don’t have to wait for your cycle to become predictable before you can start understanding it.
Your cycle can change from month to month. Fibra is designed to keep following it.
Can Fibra help me understand when my period may be coming if my cycles are irregular?
Yes. Fibra is designed to help you better understand when your period may be coming—even when your cycle timing changes.
With irregular cycles, a period date calculated mainly from previous cycle lengths can become less useful when your current cycle runs longer or shorter than expected.
Fibra adds information from your current cycle by continuously following multiple reproductive and physiological signals during wear and how those patterns change over time.
As new body data comes in, Fibra can update your expected ovulation and period timing if your cycle timing shifts, rather than keeping you tied to a date predicted earlier in your cycle.
So if your body isn’t following the timeline originally expected, your insight doesn’t have to stay stuck there either.
Instead of relying only on:
“When did my period come last month?”
Fibra adds another layer:
“What is my body doing this month—and has my timing changed?”
That can give you more relevant context about when your period may be approaching, helping you experience fewer surprises and better plan around a cycle that doesn’t always follow the calendar.
Your cycle changed. Your expected timing can change with it
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.
Fibra is designed around your personal patterns—not the assumption that everyone should have the same cycle.
Your body has its own patterns, and with PCOS or irregular periods, even those patterns may change from one cycle to another.
As you wear Fibra over time, it collects longitudinal information about how your reproductive and physiological signals change across your cycles.
That allows Fibra to build a more personalized picture of your patterns over time alongside what is happening during your current cycle, rather than treating every person as though they have the same 28-day schedule.
The goal isn’t to make your cycle look “normal.”
It’s to better understand what your patterns look like—and how they change.
What can Fibra actually tell me about what’s happening in my cycle?
Fibra is designed to turn your body signals into useful cycle insights—not leave you staring at streams of sensor data.
Rather than simply showing you five measurements, Fibra uses the reproductive and physiological information it collects to help you make sense of how your cycle is changing over time.
Depending on the current Fibra app outputs, that can include insights around where you may be in your cycle, changes in your cycle timing, estimated ovulation and fertile-window timing, and patterns in your reproductive and physiological signals.
Why does that matter?
Because when your cycle is unpredictable, you’re usually not looking for another graph. You want answers to much more practical questions:
What is my cycle doing? Has something shifted? What may be coming next?
Better understanding those changes can mean less guessing and fewer surprises, giving you more context to plan around a cycle that doesn’t always follow the calendar.
Why does Fibra track vaginal pH, discharge patterns, skin temperature, heart rate, and HRV?
Because your reproductive cycle isn’t represented by just one body signal.
Fibra combines two important types of information.
Vaginal pH and discharge patterns provide reproductive-specific information, while skin temperature, heart rate, and HRV provide additional physiological context about how your body is changing.
That matters because individual physiological measurements can also change for reasons unrelated to your cycle. Sleep, illness, alcohol, stress, and changes in routine can influence signals such as temperature, heart rate, and HRV.
Rather than relying on temperature alone or showing you five disconnected measurements, Fibra follows multiple signals and how they change over time to help build a more complete picture of what your cycle may be doing.
For someone with an irregular cycle, that’s particularly relevant because your body’s timing may change even when the calendar says it shouldn’t.
Five signals. One reproductive-health picture.
Does Fibra diagnose or treat PCOS?
No. Fibra does not diagnose or treat PCOS.
Fibra is a reproductive-wellness product designed to help you track and better understand your personal cycle patterns using reproductive and physiological signals collected during wear.
For someone with PCOS or irregular cycles, that can mean gaining more visibility into how your cycle is changing, where you may be in your cycle, and what may be coming next—particularly when calendar predictions don’t reflect your current timing.
But Fibra isn’t a substitute for a healthcare professional, diagnostic testing, or medical treatment.
If you’re concerned about symptoms, fertility, changes in your cycle, or PCOS management, speak with a qualified healthcare professional.
Fibra helps you better understand your cycle. Your healthcare provider manages your medical care.
How is Fibra different from period-tracking apps like Flo or Clue?
Period-tracking apps can be useful—but Fibra adds a different layer of information: body signals collected automatically during wear.
Depending on the app, predictions and insights can use information such as your cycle history, dates and symptoms you log, test results, or connected-device data.
Fibra is the wearable collecting its own data. During wear, it continuously follows five reproductive and physiological signals—vaginal pH, discharge patterns, skin temperature, heart rate, and HRV.
Importantly, that includes reproductive-specific signals such as vaginal pH and discharge patterns, not only general physiological information or information you enter yourself.
That difference can become especially relevant when your cycle changes. Fibra continues collecting new body data during your current cycle, allowing relevant insights to update as your timing changes.
And because Fibra collects its sensor measurements automatically, you don’t have to manually take and log those five measurements yourself.
Go beyond calendar predictions with reproductive and physiological signals from what your body is doing this cycle
How is Fibra different from Oura, Apple Watch, and other wearables?
General wearables can tell you a lot about your overall physiology. Fibra is built specifically around reproductive and cycle tracking.
Depending on the product, wrist- and finger-based wearables may collect information such as temperature, heart rate, HRV, sleep, and activity, and some also provide cycle-related features.
Fibra follows some physiological signals too—but it adds reproductive-specific signals through sensor-enabled underwear: vaginal pH and discharge patterns.
Fibra brings those together with skin temperature, heart rate, and HRV to create a reproductive-health data layer designed around understanding your changing cycle.
And because the sensing technology is built into underwear, Fibra collects those signals automatically during wear without requiring an inserted device or five separate manual measurements.
Your general wearable helps you understand your body. Fibra is built to help you understand your reproductive 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.
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