The Downside of Using Predictive Apps for Cycle Tracking

Cycle tracking apps have become very popular, and it is easy to see why. Many women love being able to customize what data lines and health metrics are included in their charts as well as the convenience of being able to update their charts throughout the day, even when they are not at home. Plus, there are countless options when it comes to what apps to use. However, some apps feature predictive algorithm technology, and it is important to understand the reasons to avoid these types of apps.


What is a Predictive Algorithm?

Apps that utilize predictive algorithms are those apps that "predict" elements of your cycle. Apps might indicate when your fertile window is going to open, when it will close, or when ovulation might occur. Algorithms vary, but these predictions may be based on your past cycle length, past fertile window, past ovulation, or they may simply be based on the assumption that you have 28-day cycle, which many women do not have. 

Note: Some apps will also predict when to expect your next menstrual period. This is less likely to be problematic, especially if the prediction does not happen until after the post-ovulatory phase has started. When the prediction is made after the luteal phase has already been established, menstrual period predictions play no role in predicting when fertility starts or ends as ovulation has already passed and the fertile window has closed.


The Problem with Cycle Predictions

The problem with cycle predictions is that they can very easily be wrong. Many things influence the cycle, with stress being a big one. Even advanced algorithms can not predict exactly how stress will affect your cycle, and the less advanced predictive algorithms are nothing more than the outdated rhythm method that uses cycle history to both open and close the fertile window.

Stress doesn’t always have to be the obvious kind either. Many women notice cycle changes during their wedding due to the added stress of preparing for the big day. Illness or travel is another common one. However, even the less obvious stressors can affect the cycle. Let’s follow a couple examples.


Disturbed Chart 2.1

 Some apps only collect data on cycle length, period data, and basal body temperature, as shown in this chart. Charting temperature is especially helpful for confirming the luteal phase has indeed started, but relying on a single parameter to determine when a fertile window closes is problematic for several reasons. Multiple things influence basal body temperature, and forgetting to mark a possible disturbance or not identifying something as a disturbance will change how a temperature-only algorithm processes the chart data. In the chart above, the temperature rise on cycle day 9 could have easily been interpreted as the start of the luteal phase, especially given that this woman has had cycles that were 25 days. If the woman did not connect the temperature rise to her warmer sleeping environment or forgot to mark the temperatures as disturbed, an algorithm could have indicated that her fertile window had closed before her temperature dropped back down again to alert her that something was amiss.


Disturbed Chart Series

 In a second example, this woman has a typical cycle range of 26-30 days and has been charting for almost a year. Her cycle typically fits well into app algorithms because her cycle consistently looks similar to the one shown on the left. The Completely Infertile Time began in the evening on cycle day 15 for this chart based on the Sympto-Thermal Rule.


 Disturbed Chart3The very next cycle, the woman's sister came from out of town to visit for a week. The women gets along well her sister and was able to keep her typical daily routine during the visit. She didn't feel stressed, her waking time was the same, and none of her temperatures seemed disturbed. If the woman was relying on a predictive app, she may have expected her Completely Infertile Time to begin around cycle day 15 again. Looking at this chart, however, this woman's days of peak fertility fell within the range of what is normally her infertile time. 

Disturbed Chart2


Based on the Sympto-Thermal Rule, the Completely Infertile Time actually began in the evening on cycle day 27. 



The Big Picture

These are just two examples of events that may affect a cycle or algorithm interpretations, but there are many more. In the first example, the temperature-only rules could have incorrectly indicated that the fertile window had closed if the temperatures were left as is. If the temperatures had been marked disturbed, the app may have struggled to apply an algorithm to the actual temperature rise later in the chart because of the location of the disturbed temperatures. Additionally, there are no options for helping a woman know when the fertile window is opening at the start of a cycle since the temperature can only confirm when it has closed, making these apps especially restrictive for women with long or irregular cycles.

In the second example, the woman's cycle length was 8 days longer than what her typical range is, which is quite a big difference. Less obvious events may affect a cycle in more subtle ways and result in a longer cycle, a shorter cycle, or even just a short luteal phase. If either of these women had simply relied on an algorithm to tell them when they were likely to be fertile or not without understanding how to accurately observe, chart, and interpret their own fertile signs, they'd be missing out on all of the benefits that come with having your cycle data. Additionally, they wouldn't be using a very effective form of family planning.

For some couples, that may be a chance they are willing to take. However, there are several fertility awareness-based methods of family planning that are highly effective and easily available today. Most of the rules taught in the SymptoPro method are over 99% effective, but working with an instructor to ensure that you fully understand those rules and how to apply them is the key. An app's algorithm should not replace fertility education or a couple's own ability to interpret and make decisions based on their cycle tracking data.


Whether you learn online or in-person, every SymptoPro Fertility Education course pairs you with a personal instructor who will be there to guide you every step of the way!  Learn Online Today or check our Find and Instructor page to see if we have a certified instructor in your area.