We’ve been waiting to share this with you for a long time: the first findings from Ava’s clinical study have been published in the peer-reviewed journal Scientific Reports.
The paper focuses on one of the nine parameters that Ava measures: resting pulse rate, and describes how it supports the identification of the beginning of the fertile window.
This is really big news: it makes Ava the first fertility tracking device to use resting pulse rate data (in combination with other parameters) to identify the fertile window. The benefit of incorporating resting pulse rate into Ava’s fertility tracking algorithm is that it is one of the earliest signs that the fertile window has begun.
We encourage you to read the study for yourself, but in case you’d prefer the Cliff Notes version, read on!
Summary of Findings
A significant increase in pulse rate during the fertile window compared with the menstrual phase (2.0 beats per minute) was observed. Additionally, pulse rate during the mid-luteal phase was significantly elevated compared with the fertile window (1.5 beats per minute) and the menstrual phase (3.3 beats per minute).
The study also demonstrates the robustness of pulse rate correlation with the menstrual phase given a broad spectrum of menstrual cycle duration, under a range of different daily activities such as the consumption of coffee, alcohol, and large meals before sleep as well as other activities such as sports, showers, and intercourse or on the background of different BMIs.
How many women were included in the study?
Ninety-one healthy, non-pregnant women between 22 – 42 years old were recruited for a prospective-observational clinical trial. 274 ovulatory cycles were recorded over the course of the study.
What’s so significant about these findings?
This study is that this is the first time anyone has tested a convenient, at-home method for using pulse rate to identify the fertile window. We asked whether it was possible to use a PPG sensor in a wearable device to give women an easy way to monitor this information themselves, and we found that the answer was yes.
Previous studies have observed a connection between resting pulse rate and phase of the menstrual cycle, but none of the earlier studies utilized wearable sensor technology, and the measurements were all conducted in clinics, which does not reflect the normal conditions for the majority of individuals interested in fertility monitoring.
Also novel in our study is the demonstration that the association between the elevated pulse rate of the ovulatory phase is observable even in irregular cycle lengths.
What causes the increase in resting pulse rate during the cycle?
We do not directly observe hormone levels in our study so we can only speculate. We suspect that the rise in estradiol at the beginning of the fertile window is related to the increase in pulse rate, but our main objective was to observe and document the behavior of pulse rate, not to establish any causality.
There is a lot of variation from woman to woman and cycle to cycle. How do you know that pulse rate always behaves in this way?
The study demonstrates the robustness of pulse rate correlation with the menstrual phase given a broad spectrum of menstrual cycle duration, under a range of different daily activities such as the consumption of coffee, alcohol, and large meals before sleep as well as other activities such as sports, showers, and intercourse or on the background of different BMIs.
The study also demonstrated the same association between the elevated pulse rate of the ovulatory phase compared to menstrual phase in irregular cycles. Despite the participants reporting regular cycle length during recruitment (cycles between 24 – 35 days), 56 of the cycles (15 percent) collected during the study were below or above that range. We analyzed these 56 irregular cycles separately to assess whether the same associations could be observed.
Indeed, we observed the same significant increase of pulse rate between the fertile window and the menstrual phase, however the magnitude of the increase was marginally smaller. The increase of pulse rate between the mid-luteal phase and the menstrual phase was also minimally reduced. However, this difference could be attributable to the smaller number of irregular cycles at hand.