Basal body temperature is measured immediately after you wake up and before you get up. It is not necessary to measure at the same time every day. The measuring time should be recorded in the cycle sheet. The measurement of the basal body temperature is necessary to identify the hormone-related rise in temperature.
Basal body temperature is the resting body temperature immediately after waking up. Before measuring, the woman should have slept or rested for 1 hour. The 6-hour sleep duration required in many information sheets is not necessary. During the learning phase, you should measure the wake-up temperature every day to know your temperature curve and its potential for interference.
The measurement can be done in different ways: rectally, vaginally, or orally.
The rectal measurement is the least susceptible to interference. With a standard mechanical thermometer, the measured value is reached after 3 minutes.
Oral measurement is more prone to failure, and correct use must be learned. The thermometer should be placed directly on the ribbon under the tongue, and the mouth should be kept closed for about 5 minutes when measuring with a regular thermometer. The temperature curve of an oral measurement runs an average of 0.2 ° C parallel to the rectal measurement.
Many women currently favor vaginal measurement. The measurement time is also here 5 minutes. Make sure that the thermometer does not slip out of the vagina during the measurement. Here, too, the measured values are slightly below the values of the rectal measurement.
Recently there have been electronic measuring systems for vaginal temperature measurement.
With a vaginal measuring system, the basal temperature can be measured automatically during the night. A tampon-like encapsulated measuring chip is inserted into the vagina before bed and removed in the morning. To read off the temperature, the course of the measured values is read out into the computer via an adapter, which is not necessary daily due to the large data memory.
The axillary measurement is too imprecise and not suitable for NFP.
All measurements should be documented in a cycle sheet that can be compared over several months.
Which thermometers should you use?
The most reliable method is with an ordinary, mechanical thermometer that is safe to use because it no longer contains mercury these days. The material is very durable, and the temperature is very precisely determined. After the measurement, it is necessary to knock the liquid in the thermometer down again by tapping it lightly.
Using the digital thermometer shortens the measurement time. When the temperature is reached after 3 minutes, an acoustic signal sounds, some digital thermometers have a measured value memory. Since the digital thermometer was primarily developed to measure fever, one should ensure with the many available offers that temperature differences of 0.05 ° C are indicated and that CE certification is available. In the case of digital thermometers, an aging process of the materials and the battery was found, which no longer gives accurate measurement data after a long period of use.
The basal temperature method (temperature method) describes a procedure for differentiating between infertile and fertile days by daily measurement of the morning body temperature, which drops by at least 0.2 ° C shortly before ovulation and increases significantly by 0.5 ° C after ovulation. Suitable for women with a regular cycle and a relatively stable lifestyle and then also a safe method of contraception.
Execution. The body temperature is measured every morning simultaneously – before getting up (basal temperature) – and entered in a cycle table or a curve sheet. The measurement can be made in the mouth, in the anus, or the vagina, but the selected part of the body must always be the same.
Basal body temperature curve
Basal body temperature curve. Practical aid for recognizing the “dangerous” days is the basal temperature curve: In the first half of the cycle, the temperature is slightly lower than in the second and falls by ~ 0.2 ° C before ovulation. The temperature rises immediately after ovulation. The level of the first half of the cycle rises again because, from this point, the hormone LH is released from the brain. If the temperature rises significantly by ~ 0.5 ° C, the woman is sterile from the 3rd day. In addition to contraception, the basal temperature method is also used to diagnose infertility (sterility diagnosis).
Safety. With a Pearl Index of around 2%, it is a safe method of contraception. The disadvantage is that stress, infections, certain medications, too little sleep, or excessive alcohol consumption affect the body affect the temperature and the method becomes unsafe. To increase safety, it, therefore, makes sense to combine it with the cervical mucus method.
What is the basal body temperature method?
The basal temperature, also known as the wake-up or ovarian temperature, is the body temperature in the morning before you get up. The body’s base temperature changes during the cycle, so measuring basal body temperature helps couples plan their families naturally. Taking your basal temperature regularly in the morning can help you determine when you ovulate and when you are fertile.
Overview of the four phases of basal body temperature and classification in the woman’s monthly cycle: 1
Phase 1: From the start of the monthly menstrual period until ovulation (ovulation), the basal temperature remains at a constant value (approx. 36.6 degrees Celsius).
Phase 2: Immediately before ovulation, the temperature drops by about 0.2 degrees Celsius. The lowest value before the sudden temperature rise usually shows you the day of ovulation.
Phase 3: On the day of ovulation or often one day afterward, the basal temperature rises by leaps and bounds by the hormone progesterone by 0.3 to 0.5 degrees Celsius. It is during ovulation that fertilization is most likely.
Phase 4: The increased temperature remains until the next menstrual period and only slowly decreases again at the end of the cycle.
The days immediately before and the day of ovulation itself are considered fertile. On average, women are fertile for five days in a cycle.2 If you have sex during this time, you are most likely to become pregnant. The phase from the third day after the temperature rise until the start of the next menstrual period is considered to be sterile. 3