A Dive Into Resting Heart Rate and the Menstrual Cycle

I purchased a Fitbit device close to two years ago, and within months I noticed that my heart rate appeared to be correlating with the phases of my cycle. Now eighteen cycles into comparing my heart rate to other fertility signs, I can say with confidence that it has lined up every cycle. This shouldn’t be too surprising because we already know that progesterone causes basal body temperature to rise, but heart rate does not exactly follow that pattern.

We have known about the possible connection between heart rate and the menstrual cycle for over a century, but in the last 50 years a few studies have taken a closer look.

Palmero (1991) studied 64 women for 3 consecutive months and created a PMS group versus a non-PMS group. They found that “in the premenstrual phase, PMS group showed significantly higher resting HR levels than NPMS group.”

Moran (2000) followed 26 women and found that “resting-heart rate was significantly higher in both ovulatory (P < 0.01) and luteal (P < 0.01) phases than in the menstrual and follicular phases.”

Shilaih (2017) followed 91 women and found that they “observed a significant increase in pulse rate (PR) during the fertile window compared to the menstrual phase (2.1 beat-per-minute, p < 0.01). Moreover, PR during the mid-luteal phase was also significantly elevated compared to the fertile window (1.8 beat-per-minute, p < 0.01), and the menstrual phase (3.8 beat-per-minute, p < 0.01).”

I want to highlight these last two studies in particular, because many of the other studies have an issue. Marco Altino explains why:

“The great majority of studies looking at HRV and the menstrual cycle collected one single data point during the follicular phase and one single data point during the luteal phase. I don’t have to tell you how little sense that makes, considering the high day to day variability in these parameters.”

This is an excerpt from his blog on heart rate variability in the menstrual cycle. Read the full blog here.

The 2017 study published in Nature by Shilaih, et al found that heart rate may rise up to 5 days before ovulation occurs. This means that heart rate could potentially be a used as a way to time intercourse for conception.

My results are so steady with resting heart rate that I dream of someone using it in a long-term study with other fertility signs. Wouldn’t it be cool if we could avoid pregnancy using heart rate too?

Below is an example of my results with resting heart rate. To convert my heart rate to fit in a fertility awareness app, I use a conversion. Essentially, one heart rate beat = .1 Farenheit change on my temperature scale. A heartbeat of 69 becomes 96.9, 70 becomes 97.0, 71 becomes 97.1 This preserves the original ratio, and it allows me to show the data with other fertility signs. For your own conversion, you may model this. If you have a lower heart beat rate, you can still convert, but you may need to do an additional equation.

My resting heart rate rose during the most fertile days of the cycle. Ovulation most likely occured on Cycle Day 15 or Cycle Day 16 on this chart. In addition, while I have not found evidence of this in the literature, I have observed that I tend to get a one day rise 3 to 4 days before the fertile window opens with cervical mucus. On this chart, that was Cycle Day 6.
A second example. Ovulation most likely occured on Cycle Day 14, 15 or 16. Heart rate rose on Cycle Day 14.

In conclusion, I believe that resting heart rate is a very unique sign to track, especially if you already use a wearable fitness tracker. I will note that a false heart rate rise can be caused by illness, alcohol or food close to bedtime, nightmares, and more! This is not dissimilar to what can obscure a temperature. I hope that in the future more studies are done so that we can see if heart rate can also be used for avoiding pregnancy purposes.

Selected Heart Rate Study Citations

Moran, V. H., Leathard, H. L., & Coley, J. (2000). Cardiovascular functioning during the menstrual cycle. Clinical physiology (Oxford, England)20(6), 496–504. https://doi.org/10.1046/j.1365-2281.2000.00285.x

Palmero, F., Choliz, M. Resting heart rate (HR) in women with and without premenstrual symptoms (PMS). J Behav Med 14, 125–139 (1991). https://doi.org/10.1007/BF00846175

Shilaih, M., Clerck, V., Falco, L. et al. Pulse Rate Measurement During Sleep Using Wearable Sensors, and its Correlation with the Menstrual Cycle Phases, A Prospective Observational Study. Sci Rep 7, 1294 (2017). https://doi.org/10.1038/s41598-017-01433-9

In Defense of Mucus-Only Methods (Specifically Billings Ovulation Method)

In the fertility awareness world, there are many misconceptions about mucus-only methods. While I cannot speak to mucus-only methods that I have not trained in, I can speak for what I have learned in training in the Billings Ovulation Method. There is so much history of the development of the method that I cannot touch on everything here. For those wanting to learn more, this document goes over some of the history of the method. Outside of that, WOOMB has many useful links.

First and foremost, the usual criticism leveled at mucus-only methods is that they have a low efficacy rating when compared to the sympto-thermal method. However, this is much more nuanced than it may appear at first glance. Let’s look at the most often quoted study for Billings.

This section of statistics is copied directly from a WOOMB International breakdown found here:

1976-78 an independent trial was conducted by the WHO, in five countries (India, the Philippines, New Zealand, Ireland and El Salvador).

This study had two phases:  
869 couples entered the three-month ‘teaching phase’,
725 couples continued in the 13-cycle ‘effectiveness phase’,
with a total of 10,215 cycles in the entire study.

The teaching phase showed that in the first cycle of charting, 93.1% of women were able to record an identifiable ovulatory mucus pattern denoting fertility, and that by the third cycle of charting, 97.1% of women had an excellent or good interpretation of the method.

The results for the entire study were:
2.2 pregnancies/ hwy    (per 100 woman years)  –  method-related pregnancy rate
22.3 pregnancies/hwy  (per 100 woman years)   –  total pregnancy rate

The total Pearl Index  – 22.3/hwy  comprised:
• Conscious departure from the rules of the method: 15.4/hwy.
• Inaccurate application of instructions: 3.9/hwy.
• Method failure: 2.2/hwy.
• Inadequate teaching: 0.3/hwy.
• Uncertain: 0.5/hwy.”

The first thing you should notice is that perfect use was 97.8%. This is pretty high. The second thing you should notice is that typical use includes people who knowingly broke the rules! All typical use always includes this. This statistic of 22.3% typical use failure is used to scare folks away from mucus only, especially when compared to one specific sympto-thermal trial by Sensiplan. However, the Thyma double check sympto-thermal had a 35% typical use rate in one trial. No method is impervious to bad typical use rates because this is dependent on how open someone is to pregnancy, as well as cultural factors. This is a flaw (depending on your perspective) of all FABM methods; someone can choose to achieve pregnancy because fertility is not suppressed.

The next thing to consider is that the older statistics of the Billings Method were based on a different peak rule, a very similar peak rule to which all sympto-thermal methods have adapted. As Billings continued to develop, the method was strengthened by over 850,000 hormonal assays completed by Dr. Brown which tested estrogen, follicule-stimulating hormone, progesterone, and luteinizing hormone. These tests were matched to Billings Ovulation Method charts. The method has been scientifically validated in over 10 total trials.

As the method was studied, the peak rule was changed to help women recognize patterns of fertility and infertility. They discovered when the specific peak rules were met, a changing and developing pattern of discharge and sensation <more specific rules apply to this>, ending at a slippery sensation felt at the vulva 《with walking sensation》and followed by an abrupt change to no longer slippery or wet, that a woman could detect a false mucus patch build up without the need for temperatures. Because of the science that Dr. Brown, Dr Evelyn and John Billings, and Dr. Odeblad verified through numerous studies, they were able to strengthen the mucus only method enough to no longer rely on temperatures without fear of double peaks. The most recent Billings study in China found a 100% perfect use rate and a 99.5% typical use rate when users were very strictly avoiding and highly motivated with the rules.

In short, the Billings Ovulation Method is very effective and for careful charters does not suffer the problem of false peaks. Again, I have barely scratched the surface of all the trials and science involved. I recommend researching Erik Odeblad and the pockets of shaw for more information.

So why do mucus-only methods get such a bad wrap? In the secular communities, I think there are a few main reasons.

1. The methods must be learned through a teacher. Learning these methods takes dedication and regular live (or online) meetings with a real person. Most folks don’t feel like making this effort or think they can’t afford it. Billings has a policy to never turn anyone away in need. Many do free services or payment plans when asked. There is also a charity associated with Billings that can sponsor Catholic couples to help them afford classes.

2. The next reason is that many sympto-thermal users have fundamental misunderstandings of what Billings is. As a certified sympto-thermal teacher and someone who has read about fifteen books on sympto-thermal, it is dissapointing how much of the original science of fertility and the cervix is left out of our materials. My mind was blown when I discovered how things really work when learning a mucus only. From the pockets of shaw to the functions of the cervical crypts, there is so much to learn that is not included in Taking Charge of Your Fertility. This does a great disservice to sympto-thermal charters.

3. Due to these misunderstandings, they think the method cannot be used by those with irregular cycles. They also may think that a non dry basic infertile pattern is not possible due to a misunderstanding of the science of the cervical plug and the effect of estrogen in the vagina.

Potential Cons of Mucus Only:

I do not say any of this to say that the Billings Method is right for everyone. It takes dedication and a willingness to follow the rules if strictly avoiding pregnancy. In addition, there are a few cons to mucus only.

1. A yeast infection or bacterial vaginosis would obscure observations and cause abstinence. However, arguably even a sympto-thermal user would need to abstain when they have an infection.

2. Women who are careless with mucus observations may end up with an unintended pregnancy. If you don’t want to track mucus carefully, this is not the right method for you. If you can’t follow the rules to safely have intercourse, such as evenings only during basic infertile pattern on alternate evenings in the pre-ovulatory time of the cycle, this method may be too restrictive for you.

3. A weak mucus patch that does not fulfill the stringent peak rules may cause more abstinence without a temperature shift to confirm. However, this often signals a potential health issue and should be investigated.

4. Mucus only methods do encourage abstinence when avoiding pregnancy. However, most sympto-thermals do the same. Anyone who is okay with an elevated risk due to barriers or alternative protected sex can always do what they want to do but should be prepared to face the consequences if a barrier method fails.

Conclusion:

Mucus only methods can be highly effective choices for avoiding pregnancy. Recent trials of Billings consistently show 99% or better with perfect use. In some cases, they may reduce abstinence because they allow women to identify false mucus build ups that do not lead to ovulation and non-dry basic infertile patterns. For women who want to eliminate barrier method usage, they offer a way to identify fertility in real time when in irregular cycles due to PCOS, postpartum, or perimenopause. This eliminates much of the extended abstinence or barrier method usage that sympto-thermal users may experience.

An Honest Review of Pearl Fertility Kit

I tried the Pearl Fertility Kit. During my first kit, I got a little confused when the kit did not seem to line up with my fertility signs. However, I contacted Pearl Fertility and they were super helpful. They sent me another kit for free, and it worked perfectly when I tried it this last cycle.

Pearl is a product marketing to women who are trying to conceive (TTC). The product explicitly states that it should not be used to avoid pregnancy. The kit contained 15 follicle stimulating hormone (FSH) strips, 15 luteinizing hormone (LH) strips, and 4 progesterone (PdG) strips. It also included a few pink dye pregnancy tests. As I am not currently trying to conceive, I did not use these.

The app claims to open a woman’s fertile window by scanning the FSH and LH strips and giving you a fertility window from these results.

If anyone wants to try this product, I highly suggest tracking your cervical mucus, as good quality cervical mucus (eggwhite, clear, stretchy, wet) is what allows sperm to survive to meet an egg. Progesterone tests need not be used until at least 4 days past your peak day (the last day of good quality cervical mucus). Even then, some women do not see positive progesterone tests until as late as 7-10 days past ovulation. For more information, visit Proov’s website linked at the end of this article. By charting your real fertility signs, you could use these tests more wisely.

Overall, I thought the Pearl Fertility Kit was super cool. FSH strips are a brand new thing, and I have high hopes for them being integrated into a real fertility awareness based method in the future. If you have the money to invest in Pearl, this can be a fun kit to experiment with. Basically you get to see three main hormones of the menstrual cycle play out. Pearl graphs them for you.

If you cannot afford Pearl, do remember that it is free to chart cervical mucus and that this is always the best indicator for when to have sex when trying to achieve pregnancy. Without cervical mucus, sperm will never make it to the egg on its own.

Here is what my Pearl chart for this month looks like:

The highest pink dot is my positive LH strip.

Here is my Pearl information compared to my symptothermal method chart. In this chart, FSH equals Ferning since Kindara does not have an FSH category.

The Pearl fertile window is indicated by the green lights. It did start my fertile window on a day pregnancy was unlikely since there was no mucus. The blue hearts represent the fertile mucus where sperm can survive. These two fertile windows lined up pretty well.

Overall, I would rate myself satisfied with this kit.

One tip:

From the calendar screen, you can override what tests Pearl is asking for. I only suggest doing this if you are charting your other fertility signs (cervical mucus and basal body temperature) and know that something is not lining up right.

In addition to the strips, Pearl has spaces to track intercourse, your period, and pregnancy status.

Curious to know more about the fertility signs?

If you want to learn how to chart your real fertility signs to achieve or avoid pregnancy, read my guide to getting started.

Look for my next blog on using Proov progesterone tests.