Testing Natural Cycles & Mira: My First Experience Beyond Creighton NFP

As an NFP-only Family Medicine physician, I work with couples that use all different methods of natural family planning (NFP). While my personal experience has always been rooted in Creighton, I’ve been curious to explore how more modern apps such as Natural Cycles and Mira measure up in real life. Many of my patients and readers use these apps, and as a trusted fertility advisor, I wanted to test them for myself to give informed guidance.

For three months (May - July 2024), I continued my Creighton charting while also using Natural Cycles and Mira. My goal was to see how these different methods compared in terms of ease, accuracy, and overall experience. Here’s what I discovered during this hands-on experiment with each approach, and how they stack up against the tried-and-true Creighton method.

As a disclaimer, I did not get paid by Natural Cycles or Mira to do this experiment or write this blog.

Just to give some background, I started learning how to chart with Creighton in the beginning of 2021 while in marriage prep. My husband and I chose to learn the Creighotn method for several reasons. One reason in particular was because I was in residency and had a very fluctuating schedule. I could not rely on waking up at the same time every morning to check my basal body temperature (BBT) or urine hormones since my schedule would change from month to month, and I would have to do a 24-hour shift at the hospital at least once weekly. Additionally, we liked that Creighton didn't require us to keep buying supplies such as urine test strips to keep up with charting. Finally, I planned to eventually get trained in NaPro Technology myself in order to become a Creighton FertlityCare Medical Consultant, so I thought already using this method would make that process even easier. As of now, my husband and I have been using Creighton to avoid pregnancy for the past 3 and a half years while completing residency and trying to get settled in a new city and job post-residency. We have never personally explored the sympto-thermal or sympto-hormonal methods of NFP.

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Table of Contents:

Understanding What You are Looking at

Cycle 1 Charts

Cycle 2 Charts

Cycle 3 Charts

Comparing the Actual Data

Overall Experience with Each

Conclusion

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Understanding What You are Looking at:

In order to compare Creighton, Natural Cycles, and Mira methods I lined each chart up to compare them over the course of a cycle. The start of a menstrual cycle is the first day of a woman's period, and the entire cycle lasts until the start of her next period. The fertile window is the start of fertility leading up until ovulation has occurred and been confirmed. Twenty-four hours after ovulation has occurred, a woman can not become pregnant. Natural Cycles (basal body temperature method) is the chart on top, which measures the body's basal body temperature while asleep. The fertile window is shown in red when temperature is low, and the chart turns green when ovulation has been confirmed with raised BBT (0.15-1.0 degrees F). Mira is the chart on the bottom. We can assume that ovulation occurs after LH (luteinizing hormone) levels have spiked. This can be seen when the turquoise line spikes. The additional lines within the Mira chart indicate other hormone levels (black is for estrogen levels, and purple is for progesterone). Creighton is the chart in the middle. The grey squares indicate the start of the fertile window, which is identified by the first observations of fertile cervical mucus (clear, stretchy, lubricative). The last day of fertile mucus observation marks peak day (indicated by "P"), which is thought to be when ovulation occurs.

When comparing these charts, try to notice the start of fertile windows, and the peak day/ovulation days as noted by each method. We are going to compare the different methods in regards to their ability to identify peak day (ovulation) and fertile window.

Cycle 1:

Cycle 2:

Cycle 3:

Comparing the Actual Data:

I collected all of my data from Creighton, Natural Cycles, and Mira and placed them into various charts to analyze the data. I looked at the accuracy of being able to identify peak day, the start and end of the fertile window, and the overall cycle length for each method. I looked at the average amount of days that Natural Cycles and Mira varied from Creighton. For example, if Natural Cycles thought that the peak day was 14, Mira thought peak day was on day 16, and the actual peak day (Creighton determined) was on day 15, they both would be 1 day variation from Creighton.

Comparing Peak Days:

Cycle #	Natural Cycles Peak Day	Mira Peak Day	Creighton Peak Day
1	21	20	19
2	17	17	16
3	18	15	18
Avg variance from Creighton	1	1.67

Although both apps were fairly close, it looks like Natural Cycles was slightly better at being able to determine peak day. On one hand, Natural Cycles was either right on with Creighton's peak day, or overestimated by a couple of days. On the other hand, Mira had 1 cycle that actually underestimated the peak day by 3 days. While overestimating will end up giving you a longer fertile window (and thus less days for intercourse during your cycle if you are trying to avoid), underestimating the peak day puts a woman at risk of conceiving when trying to avoid pregnancy. This is due to falsely thinking that she has already ovulated and therefore out of her fertile window.

Comparing the Start Day of the Fertile Window:

Cycle #	Natural Cycles Fertile start	Mira Fertile Start	Creighton Fertile Start
1	6	16	12
2	6	13	11
3	7	11	13
Avg variance from Creighton	5.67	2.67

Although it was not perfect, Mira appeared to be superior at identifying the start of the fertile window when compared to Natural Cycles. This is likely due to the fact that Mira does not simply "predict" when the fertile window starts, but it identifies it in real time by measuring the amount of estrogen within the urine. At the start of each cycle, Mira will give its prediction of when it thinks the fertile window will begin, but it adjusts as you go throughout the cycle and urine hormone levels are measured. On the other hand, Natural Cycles only relies on an algorithm to predict when the fertile window will start. I believe that if I would have used the Natural Cycles app for longer than just 3 cycles, it would start to give a bit better of a prediction. However, it still is only a prediction, which can be problematic, even for a woman with the most regular cycle, since many factors such as stress can cause one cycle to be completely thrown off. If this was the case, relying on a prediction of when your fertile window starts could mean that a woman could think that she is still in the non-fertile days of her follicular phase and be having intercourse while actually within her fertile window. Therefore, women choosing to use basal body temperature (BBT) apps need to also incorporate another method such as making cervical mucus observations to be able to accurately identify the start of the fertile window, and then BBT can be used to confirm ovulation has occurred and the fertile window has closed.

Comparing the End of the Fertile Window:

Cycle #	Natural Cycles Fertile End	Mira Fertile End	Creighton Fertile End
1	22	22	22
2	19	19	19
3	19	17	21
Avg variance from Creighton	0.67	1.33

Natural Cycles reigned supreme when compared to Mira for being able to identify the end of the fertile window. However, this was a very close race since both Natural Cycles and Mira accurately pinpointed the end of the fertile window to be the exact same day as the Creighton method during the first 2 cycles of this experiment. The third cycle is where we saw both Natural Cycles and Mira were unsuccessful at identifying the end of the fertile window, but Natural Cycles still appeared to be closer.

Comparing the Length of the Fertile Window:

Cycle #	Natural Cycles Fertile Length	Mira Fertile Length	Creighton Fertile Length
1	17	7	11
2	14	7	9
3	13	7	9
Avg variance from Creighton	5	2.67

The clear winner for cycle length was Mira. Natural Cycles tended to have cycle lengths that were approximately twice as long as Mira's. Much of this can be attributed to the fact that Natural Cycles uses an algorithm to determine the start of the fertile window. Since I only used Natural Cycles for 3 cycles, it did not have long enough to adjust its algorithm to my average cycle. Therefore, it would start each fertile window immediately after my period had ended. Unlike Natural Cycles, Mira actually analyzes your fertile signs in real time to not only identify when ovulation has occurred, but to also be able to identify when the fertile window has begun.

Overall Experience With Each:

Natural Cycles:

One thing that would frustrate me about Natural Cycles was that there were times when I had forgotten to charge my watch prior to going to bed. When this would occur, I just would not be able to track my BBT that night, which could mean that I was missing an important data point. Granted, I appreciate that the Natural Cycles app sends you reminders as you are getting closer to bedtime to charge your watch. However, there were still times that I might not have gotten home with enough time to charge my watch before going to bed.

I really enjoyed the ease of just using my Apple watch since I wear this all day and all night anyway. There really was not too much more I had to think about doing for this method other than keeping my watch charged. I also really liked being able to confirm that ovulation had occurred while still using Creighton. I can see Natural Cycles helping women, who second guess their own cervical mucus observations, become confident in their ability to make these observations since they would have the BBT to verify that they did, in fact, reach peak day.

I would be interested to see how the app's fertile window predictions change the longer you use it. Since I did not use the app very long (only 3 cycles total), I never got to see a good example of how its algorithm works at making this prediction. Typically the app would just tell me that as soon as my period was done, I was entering my fertile window.

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Mira:

One of the things that was most frustrating about Mira was having to make sure you got your first morning urine. While in most cases this was not difficult to do, there were a few occasions when I would wake up having to go to the bathroom in the middle of the night. I would have to decide if I should just test my urine at that time, or if I should just wait until the morning. Plus you are not supposed to have anything to drink for at least 2 hours prior to testing your urine. This also became an occasional challenge because I would be scared that getting a drink of water in the middle of the night would throw off my urine hormone levels the next morning.

Additionally, my first day of using Mira I had an issue with the monitor itself. For some reason it was programed as a different date on the monitor itself. I could not figure out how to fix it that morning, so I had to do a factory reset of the monitor to get the date on the monitor to match up with the actual date and therefore sync correctly with my phone app.

However, on a positive note, I loved being able to actually see the change in my hormone levels throughout my cycle. Seeing numerical values and being able to check if hormones such as my progesterone were falling within a normal range was very reassuring. Having access to more information about one's cycle can give women more knowledge about their body and give some relief if they were afraid of hormonal irregularities. That being said, I still think it is best to discuss your cycle and chart with a Natural Family Planning (NFP) physician who can better interpret any changes and check actual blood tests for more precise hormonal levels.

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Creighton:

I may be biased since I have been using Creighton for over 3.5 years, but if I had to chose only one method to use, it would be Creighton. I love the ease of this method and appreciate not having to remember to bring certain monitors/strips/chargers with me when traveling. It doesn't rely on time of day for observations like first morning urine for Mira. It isn't influenced by alcohol or illness like Natural Cycles. I can use this method anywhere and at anytime. However, I definitely see the draw to the other methods as well, especially since it can take several cycles to become confident with making cervical mucus observations through Creighton. I personally loved being able to see more objective data about my cycle with both Mira and Natural Cycles.

Conclusion:

Overall, I had a lot of fun getting to try out different methods of NFP since my only previous experience was using Creighton (a cervical mucus method). I enjoyed seeing the objective data about my hormone levels and ovulation, which added another layer of insight to my cycle that I hadn't experienced with Creighton alone.

After three months of testing, the comparison between Natural Cycles and Mira to Creighton offered some valuable insights into each method’s strengths. Mira excelled at pinpointing the start of the fertile window and providing a more precise idea of its overall length, giving me a deeper understanding of my cycle’s hormonal patterns. On the other hand, Natural Cycles was highly effective at identifying peak day (ovulation) and determining the end of the fertile window, which helped me feel even more confident in tracking my cycle’s key phases.

In the end, I would recommend Mira over Natural Cycles, especially if you are trying to avoid pregnancy, because Mira has the ability to actually identify the start of your fertile window on its own. Using Natural Cycles alone would not be able to accurately identify the start of your fertile window and would require you to use another method in combination with Natural Cycles. However, if you are willing to also learn a cervical mucus method along with Natural Cycles, then Natural cycles would be a preferred option for women due to ease of use, being cheaper overall, and being better able to identify peak day. Natural Cycles is a nice supplement to use alongside cervical mucus observations.

While each method has its unique strengths, my experiment reinforced the idea that different NFP methods can serve different needs. For those looking to integrate technology into their NFP practice, both Natural Cycles and Mira offer valuable tools that complement cervical mucus methods like Creighton. I would say that the most important thing is to pick a method that best suits your personal lifestyle, find an instructor to teach you that method properly, learn all of the protocols associated with each, and then stay consistent. As always, also be sure to find an NFP physician, so that they can interpret your chart properly and look into further evaluation and treatment for any cycle irregularities.

Click here to read my blog post about how to choose which method of NFP is best for you.

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