… your basal body temperature changes by 0.2°C over the course of the cycle, and that with this knowledge you can find your fertile days?
What you will find on this page:
- What is the temperature method?
- Why does the temperature change?
- How does the temperature method work?
- Advantages and disadvantages of the temperature method
- How reliable is the basal body temperature method?
- Combining it with other methods
- Comparison of the temperature method and the symptothermal method
What is the temperature method?
You can use the temperature method both for hormone-free contraception and when trying to conceive. It is one of the methods of natural family planning (NFP) and is based on the rise in temperature after ovulation1. By documenting and analysing your basal body temperature, you can determine whether ovulation has taken place and when it is over. Once it is over, your temperature rises by at least 0.2°C and stays elevated for the rest of the cycle. After ovulation, the egg can be fertilised for up to 24 hours, after which your infertile phase, the second half of the cycle, begins.
If you document your temperature curve over several cycles, you can also narrow down the fertile days before ovulation more precisely. As you may already know, it is possible to get pregnant even before ovulation. You can find out how this happens in the article: How long do sperm survive? Good to know: the calendar method is the basis of most simple cycle apps that do not require any temperature readings from you.
Why does the temperature change?
A woman's cycle is governed by various hormones. These in turn affect so many things: our skin, our mood, even our sex drive. Our core body temperature is also influenced by them. This influence is not random but follows a pattern. And it is precisely this pattern that the temperature method makes use of.
How does the temperature method work?
Analysing your basal body temperature means using your temperature curve to calculate your infertile days and fertile days. For the measurement you absolutely need a basal thermometer (a clinical thermometer with two decimal places) or a cycle computer. Right after waking up, you should measure your basal body temperature. You can then enter the readings in a cycle sheet and analyse them, or use a cycle app.
The chart shows the documentation of the readings in a basal body temperature curve. You can clearly see that the cycle curve divides into a low phase and a high phase. These are also called the first and second half of the cycle. Since the temperature rise is minimal, it is important to measure to two decimal places. The basal body temperature method comes with a few evaluation rules. For example, a high phase, and therefore infertility, is only assumed once three elevated readings have been measured on three consecutive days.
Temperature method: making use of changes in basal body temperature
So that you do not have to learn these rules yourself, we recommend using the cyclotest mySense app or the cyclotest myWay cycle computer. These tools take care of the analysis for you.
cyclotest mySense not only analyses your basal body temperature reliably, you can also include your cervical mucus (symptothermal method) or ovulation tests in the analysis.
Advantages and disadvantages of the temperature method
A comparison of contraceptive methods shows that the temperature method offers numerous advantages:
The disadvantages can be summarised as follows:
How reliable is the basal body temperature method?
On its own, the basal body temperature method is less reliable for contraception than in combination with other reliable ovulation symptoms such as cervical mucus. This is because the basal body temperature only indicates that ovulation has taken place. If ovulation occurs much earlier in a cycle than in previous cycles, the "early warning system" telling you that the fertile days start sooner after menstruation this time is missing. That is why, in natural family planning used for contraception, the analysis is ideally always symptothermal, meaning the cervical mucus symptom is included.2
Combining it with other methods
The basal body temperature method is the perfect basis for natural contraception, and equally for finding the most suitable days for intercourse when trying to conceive. The following combinations work well:
Comparison of the temperature method and the symptothermal method
| Criterion | Temperature method | Symptothermal method |
|---|---|---|
| Basis | Measurement of basal body temperature | Measurement of basal body temperature + cervical mucus observation |
| Effort | Relatively low, daily temperature measurement required | Somewhat higher, as several parameters need to be documented |
The additional effort of the symptothermal method is worth it, as the fertile days and ovulation can be narrowed down even more precisely.
Sources:
- 1 Diedrich, K. et al.: Gynäkologie und Geburtshilfe. 2. Auflage. Heidelberg 2007.
- 2 Bundeszentrale für gesundheitliche Aufklärung (BZgA) (Hrsg.): Broschüre „Sichergehn – Verhütung für sie und ihn“. Köln 2013.