Is the symptothermal method reliable? What the science really says
Is the symptothermal method reliable? What the science really says
Yes. And science backs this up. When learned properly and practiced consistently, the symptothermal method is one of the most thoroughly studied cycle-tracking methods. I wanted to explain it to you simply, using the study data as a reference, without overselling it.
Reliable, yes, and like any method, in its own way
Let’s start with a frank admission: no form of birth control is 100% reliable, not even permanent methods. Each has its strengths, its limitations, and an effectiveness that depends in part on how it’s used. The rhythm method is no exception, and that’s to be expected.
What makes it unique is that it’s based on observation. The more consistent and careful your observations are, the more accurately it will guide you. Much of its reliability therefore depends on you, and that’s actually a pretty nice thing.
A quick aside to help you understand the numbers
To compare different methods of birth control, a common standard is used. We look at how many out of 100 women who use a particular method for one year experience an unplanned pregnancy. The lower this number, the more reliable the method is.
And there are always two numbers—it’s good to keep that in mind. The first represents the method followed perfectly, to the letter. The second represents real life, with all its unexpected twists and turns. To put it in a slightly humorous way: it’s the difference between the cake recipe pictured in a cookbook and the same cake that comes out of your oven on a weeknight. Both are cake—they just don’t always look the same.
Statistics on the Symptothermal Method
The landmark study followed 900 women for years, covering nearly 18,000 cycles. It focused on Sensiplan, the most rigorously evaluated German symptothermal method, which has become a benchmark in Europe. It is one of the most robust studies on the subject, and here is what it found.
When the method was followed perfectly—by avoiding intercourse during fertile days—there was fewer than one unintended pregnancy per 200 women over the course of a year. That is a very low rate, comparable to the most effective forms of birth control.
In everyday life, taking into account unforeseen circumstances, the figure was about 2 out of every 100 women per year. That’s still a very good result for everyday use.
One final statistic sheds light on everything else: when intercourse took place during fertile days without protection, pregnancies naturally became more common. This is valuable information, not a criticism: the symptothermal method tells you when your fertile days are, and it’s up to you to decide, in good conscience, what to do with that information.
And it's not just one study
A single study is never enough to be certain of anything. That is why researchers compiled and compared all existing studies—53 in total—to assess their reliability. Their conclusion aligns with the initial one: among all methods for tracking the menstrual cycle, Sensiplan is one of the most effective.
These same researchers add a candid remark: not all approaches are equal, and some connected devices are marketed as reliable without having actually been evaluated. I’d rather be honest with you about this, because what really matters isn’t the tool we use, but the quality of our day-to-day observations.
Let's compare them—that will make it clearer
To compare the symptothermal method with other forms of birth control, here is a summary table. The numbers indicate the number of pregnancies per 100 women in one year: on the left, under perfect use; on the right, under typical use. The lower the number, the more reliable the method.
| Method | Perfect for its intended use | Common usage |
| Implant | 0,05 | 0,05 |
| Hormonal IUD | 0,2 | 0,2 |
| Copper IUD | 0,6 | 0,8 |
| Birth Control Pill | 0,3 | 9 |
| Symptothermal Method (Sensiplan) | 0,4 | 1,8 |
| Temperature-Only Method | 1 | — |
| Billings Method (cervical mucus only) | 0.5 to 3 | 10 to 24 |
| Fixed-Day Method (Calendar) | 5 | 12 to 24 |
| Ogino Method (Calculation) | 4 | 27 |
| Condom (external) | 2 | 13 |
| Withdrawal | 4 | 20 |
| No method | 85 | 85 |
Figures based on data from the World Health Organization (2011), the Haute Autorité de Santé, and the Frank-Herrmann study (2007) on the symptothermal method. Values vary depending on the study and the population. The temperature-only method is poorly documented in routine use (as indicated by the dash), since it is now almost always combined with cervical mucus observation, which amounts to practicing symptothermal contraception.
What this table clearly shows is that the symptothermal method, when followed carefully, is among the most effective methods, and one of its strengths is that it combines two signs, whereas other natural methods observe only one and are slightly less reliable.
So, where does the “98%” we see everywhere come from?
You’ve probably come across this figure before. It’s accurate, but it’s a simplified and rounded way of presenting the data. It isn’t wrong—it’s just less precise. I’d rather give you the actual figures from the studies—the ones you just saw—because they convey the same message without any rounding.
And what about the pill in all this?
This comparison comes up often. The birth control pill is very effective when used correctly. In real life, its effectiveness depends on how consistently it is taken—just like any other daily routine. The symptothermal method follows the same logic: it is very reliable when used rigorously, but less so when conditions aren’t met.
A note that’s important to me: The purpose of this article is to inform you, not to recommend one method over another. Choosing a form of birth control is a deeply personal decision that should be made with a healthcare professional who is trained in these matters and familiar with your situation.
Observation is at the heart of everything
If there’s one key point to remember: the excellent results of the symptothermal method are based on careful observation, carried out day after day, using two signs rather than just one—temperature and cervical mucus. It is this combination, known as “double checking,” that makes cycle tracking accurate and reliable. This is, in fact, what sets Sensiplan apart from methods that rely on only one sign.
One point I think is worth sharing: all of these studies were conducted with women who had received training and support. It’s perfectly fine to start tracking your cycle on your own, and that’s already a wonderful journey in itself. But having guidance—especially in the beginning—goes a long way toward helping you track your cycle accurately and move forward with confidence.
Allow about three cycles to get comfortable with the process—enough time to learn to recognize your own signs. And rest assured: even this learning period has been shown in studies to be reliable, as long as it’s properly supported.
In summary
Symptothermal contraception has been proven to be reliable, provided one simple condition is met: that it is learned properly and practiced consistently. It’s not a magic solution—it’s a skill you build at your own pace. And once you’ve mastered it, it stays with you for life: you get to know your cycle, and that knowledge never fades.
Frequently Asked Questions
When followed correctly, it has shown comparable effectiveness in studies. However, the two methods are very different in everyday use, and everything depends on how consistently they are used. The choice should be discussed with a healthcare professional trained in these matters.
From a large-scale study of 900 women and nearly 18,000 cycles, focusing on the Sensiplan method, which was subsequently confirmed by an analysis of all existing studies. These are recognized scientific sources, cited at the bottom of this article.
You can start on your own, and that’s already very instructive. The studies, however, focus on women who are receiving support: having guidance at the beginning helps you observe accurately and move forward with confidence.
Generally, three cycles—enough time to learn to recognize your signs. With the right guidance, this phase is already reliable.
Sources
Frank-Herrmann P., Sottong U., Baur S., et al. “Natural Family Planning: Sensiplan—A Modern, Reliable Method.” Der Gynäkologe, 2011, vol. 44, pp. 17–22. DOI: 10.1007/s00129-010-2659-5.
Peragallo Urrutia R., Polis C.B., Jensen E.T., et al. “Effectiveness of Fertility Awareness-Based Methods for Pregnancy Prevention: A Systematic Review.” Obstetrics & Gynecology, 2018, vol. 132, No. 3, pp. 591–604. DOI: 10.1097/AOG.0000000000002784.
World Health Organization, Comparative Effectiveness of Contraceptive Methods (2011); Haute Autorité de Santé, document on contraceptive methods (2013).
