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Ava Bracelet

What Your Ava Data Means

You’ve probably heard of basal body temperature and OPKs. But the Ava Bracelet provides information that you might never have heard of before. Why does Ava measure more than just temperature?

In fertility tracking, there is a lot of focus on using urine tests and the temperature method to pinpoint ovulation. There are downsides to these methods: temperature can only tell you after you’ve already ovulated, when your fertile window is over. And LH tests only give you a very small fertile window of 12 – 48 hours, when your fertile window is actually six days long.

Changes in other physiological parameters, such as resting pulse rate and breathing rate, can help give a more comprehensive view of the cycle and contribute to earlier detection of the fertile window.

The chart below shows the typical pattern of menstrual cycle hormones. While progesterone increases only after ovulation, estradiol increases just before ovulation. The parameters that Ava measures correlate with both estradiol and progesterone.

To help you make sense of the new parameters that Ava monitors, we put together this in-depth guide.

Skin Temperature

What is it?

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Skin temperature is the temperature measured at the surface of the skin. Ava measures the skin temperature at your wrist.

What’s a normal skin temperature?

Your skin temperature is lower than your oral temperature and averages are between 90.5 – 98.2 degrees Fahrenheit.

What kind of pattern should I see in my skin temperature?

During the night, when you are in your deepest sleep, your body reaches its very lowest temperature, called your basal body temperature. Where you are in your cycle influences your basal body temperature. The classic pattern is for temperature to be low and somewhat variable in the first half of your cycle, then increase within a day or two after ovulation and remain elevated until your next period begins.

This pattern won’t look exactly the same for every woman or for every cycle, but for the majority of ovulatory cycles, there will be a clear biphasic temperature pattern. In other words, when you look at your chart as a whole, temperatures should be lower in the first half of your cycle and higher in the second half of your cycle.

What to look for in your Ava data

  1. Temperature is low and variable in the first half of the cycle
  2. Average temperature typically increases by about one half of one degree Fahrenheit within a few days after ovulation
  3. Temperature typically remains elevated until the end of the cycle

Resting Pulse Rate

What is it?

Resting pulse rate is the number of times your heart beats per minute when you are completely at rest.

What’s a normal resting pulse rate?

Typical RPR is between 40 – 80 bpm. If you are very physically active, your RPR may be even lower than 40 bpm. Stress, illness, and alcohol can cause temporary increases in RPR—as can pregnancy!

What kind of pattern should I see in my resting pulse rate?

Ava’s research partner, the University Hospital of Zurich, conducted a clinical study looking at RPR throughout the menstrual cycle. It found that in an average cycle, RPR is lowest during menstruation, but several days before ovulation, it begins to increase. It continues to increase after ovulation, reaching a peak in the mid-luteal phase.

What to look for in your Ava data

  1. RPR is usually lowest during or just after menstruation.
  2. For most women, RPR begins to rise within the five days leading up to ovulation. The exact amount of this rise can vary from woman to woman, but the average increase we found in our clinical study was a two beats per minute.
  3. For many—but not all—women, RPR continues to increase after ovulation, reaching a peak in the mid-luteal phase. For some women, RPR continues to rise after ovulation, but then falls again during the luteal phase.
  4. RPR tends to fall back down to baseline levels in the days just before or just after menstruation.

Breathing Rate

What is it?

Breathing rate is the number of breaths you take per minute (bpm).

What’s a normal breathing rate?

Breathing rate can vary widely during the course of a day due to your activities, but typical breathing rates during sleep range from 10 – 25 bpm.

What kind of pattern should I see in my breathing rate?

Several studies have shown that breathing rate is lower in the follicular phase (from the first day of your period until ovulation) and higher in the luteal phase (from the day after ovulation until the day before your next period)[2.].

What to look for in your Ava data

  • Breathing rate is lower in the follicular phase
  • Breathing rate is higher in the luteal phase

Heart Rate Variability Ratio

What is it?

Heart rate variability, or HRV, is the variation of the time gap between your heart beats.  HRV is a direct link to your autonomic nervous system and can be used as an indicator of physiological stress.

Ava measures the ratio between low frequency and high frequency waves in your heart rate. We call this number the “HRV ratio,” which is not the same as overall HRV.

What’s a healthy HRV ratio?

A universal scale for healthy HRV ratio does not exist—it varies widely from person to person. The best way to use your HRV ratio data is to observe it for one cycle to get a sense of what your personal baseline is, and then notice when you are higher or lower than normal. A lower number in the app actually indicates that you are less stressed.

Why is HRV ratio important?

Physiological stress can have a variety of impacts on your body, affecting your mood, your immunity, and even your fertility. Stress can delay ovulation, contribute to anovulation, or shorten your luteal phase.

Sometimes, you can be physiologically stressed without actually feeling stressed out. Intense exercise, travel, tiredness, and coming down with an illness can all be interpreted by your body as a form of stress—even if you feel as cool as a cucumber!


What is it?

When sleeping, your body typically goes through several sleep cycles each night. Such cycles last on average 90 minutes. You alternate between types of sleep in each cycle.

When your body is completely at rest and unmoving, Ava records that you are asleep. Ava shows the total amount of sleep you get each night. It also tracks the percentage of light sleep and the percentage of combined deep and REM sleep.

Light Sleep —Light sleep is a non-rapid eye movement (NREM) phase, with less brain activity than REM sleep.

Deep Sleep – Deep sleep is also a NREM phase. Periods of deep sleep are typically longer early in the night.

Rapid Eye Movement (REM) Sleep—The stage associated with vivid dreams, REM sleep periods are typically longer as the night goes on.

What’s a healthy sleep pattern?

Typical sleep cycles for adults are 50 – 65 percent light sleep and 35 – 50 percent deep sleep + REM.

 Why is sleep important?

The quality and quantity of sleep you’re getting each night are important parameters to track for your fertility. Pregnancy can also influence sleep. Deep sleep is important for feeling rested the next morning, while REM sleep is important for learning and storing memories.

Sleep is also important for Ava to be able to get accurate measurements. Ava measures the physiological changes that happen when your body is completely at rest. It takes at least three hours of sleep for these parameters to stabilize and for Ava to get an accurate reading. By tracking your sleep pattern, we can determine the quality of the measurements taken.


The following parameters are tracked on the back-end only, and not displayed in the Ava app:


If you’ve ever had an elastic band around your finger and felt the blood flow being cut off, you’re already familiar with the process of perfusion.

While you can limit perfusion with an elastic band, perfusion can also change naturally for different reasons. For example, your perfusion changes in order to keep you warm or cool you down.

Perfusion also changes in relation to the menstrual cycle: it is higher in the fertile days and lower during the luteal phase.


Ava tracks your movement with an accelerometer. The measurement of your movement and the different rates of change in movement allows Ava to distinguish between light, deep and REM sleep.





Lindsay Meisel

Lindsay Meisel is the Head of Content at Ava. She has over a decade of experience writing about science, technology, and health, with a focus on women's health and the menstrual cycle. Her work has been featured on The Fertility Hour, The Birth Hour, The Breakthrough Journal, and The Rumpus.

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