In Defense of Mucus-Only Methods

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. 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, follicular stimulating hormone, progesterone, and luteinizing hormone. These tests were matched to Billinge 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, ending at a slippery sensation felt at the vulva 《with walking sensation》 followed by an abrupt change to no longer slippery or wet) that a woman could detect a false mucus patch without the need for temperatures. Because of the science that Dr. Brown, Dr Evelyn and John Billings, and Dr. Odeblad discovered, they were able to strengthen the mucus only method enough to no longer rely on temperatures. The final peak rule was changed in the 1990s. Trials before this do not reflect the more stringent rules that the method requires, and thus the perfect use statistics are not as reflective of the current method. 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. However, the average Billings teacher charges around $250 for help (could be less depending on location). Billings has a policy to never turn anyone away in need. Many do free services or payment plans when asked.

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.

3. A weak mucus patch 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.


Mucus only methods can be highly effective choices. In some cases, they may reduce abstinence because they allow women to identify false peaks and non-dry basic infertile patterns. For women who want to reduce barrier usage, they offer a way to identify fertile in real time when in irregular cycles due to PCOS, postpartum, or perimenopause.

I do also want to note that Billings Ovulation Method has more rigorous training than my previous sympto-thermal training and that teachers are closely watched and constantly upskilled. I have more confidence and understanding of my fertility by charting with Billings

Published by Leslie Rewis

Hello! My name is Leslie. I'm from Alabama in the USA. I'm a fertility awareness educator and a body literacy advocate.

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