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La température corporelle basale est le thermomètre de votre fertilité
Cycle menstruel

Basal body temperature is the thermometer of your fertility

The human body, with its complexity and subtleties, has an incredible capacity to give us clues about its internal workings. Among these indices, basal body temperature proves to be a valuable indicator, particularly for menstruating people who wish to understand the rhythms of their fertility. Want to know more about TCB ? Know how to follow and understand your temperature curve ? Let's go !

Basal body temperature: what is it?

Let's dive into another often overlooked aspect of menstrual cycles: basal body temperature (BBT).

It refers to the lowest temperature reached by the body at rest, generally during sleep . It represents the internal temperature of the body when it is in a state of complete rest, without the influence of physical activities, digestion or other factors that could increase the temperature.

Measuring your temperature curve, why should you care?

The temperature curve is not simply a medical concept or a biological phenomenon. It represents a valuable tool for many menstruating people wishing to better understand their body. There are several motivations to adopt this practice. Let's discover together the different reasons which make this curve a key element of the menstrual cycle.

A natural map of ovulation

When we talk about the menstrual cycle, most of us immediately think of periods. However, behind the scenes, the female body orchestrates a hormonal ballet of which the basal temperature is a precious witness. Measuring your temperature curve allows you to identify with some precision the time of ovulation . After all, it's a bit like having a natural GPS for our fertility! Please note that the body temperature of women and people with vulvas changes throughout the menstrual cycle. Usually the body temperature is below 37 degrees Celsius. Just before the ovulation period, the temperature drops and then rises above 37°C during the luteal phase (after ovulation). In case of pregnancy, the basal body temperature remains above 37°C for at least 10 to 14 days, until the next menstruation is due.

An ally for conception... or its prevention

Whether you are planning to expand the family or, on the contrary, to prevent pregnancy, following your temperature curve is a natural method to better understand your fertility window. Of course, used alone, it does not replace medical contraception , but it provides invaluable insight into the most fertile days.

An anomaly detector

Well beyond the simple detection of ovulation, this curve can also be a warning signal. An absence of temperature rise? This may indicate a cycle without ovulation. Other irregularities could also be valuable clues to reproductive health.

Understanding the temperature curve during the 4 phases of the menstrual cycle

The body of people with vulvas is a marvel regulated by natural rhythms and hormonal variations which directly influence the basal body temperature. Understanding these thermal fluctuations based on one's menstrual cycles can offer profound insight into reproductive health and the timing of ovulation. Shall we see all this together in detail?

The menstrual phase (periods)

Duration: Approximately 3 to 7 days, although this may vary.

Basal Body Temperature: During this phase, the temperature is generally at the lowest point of the cycle (between 36.1°C and 36.5°C) , or it begins to drop to reach this low point.

👉 Periods mark the start of a new cycle. During this time, the body sheds unused uterine lining. Hormone levels, particularly estrogen and progesterone, are relatively low, resulting in a lower basal temperature.

The follicular phase (pre-ovulation)

Duration: Until ovulation, approximately 14 days in a 28-day cycle, but this can vary.

Basal Body Temperature : The temperature remains relatively stable and low during the follicular phase.

👉 This is the phase preceding ovulation. Estrogen begins to increase, which stimulates the growth of the ovarian follicles containing the eggs. Although estrogen is rising, it does not significantly affect BBT until ovulation approaches. The TBC is generally between 36.1°C and 36.7°C.

The ovulation phase

Duration: Very short, generally 24 to 48 hours.

Basal Body Temperature : Just before ovulation, a slight drop in temperature can be observed, followed by a sharp increase after ovulation.

👉Ovulation is triggered by a sharp increase in luteinizing hormone (LH). This is the time when the ovary releases a mature egg. The rapid rise in BBT reflects the shift from the estrogen-dominated cycle to a progesterone-dominated phase. After ovulation, there is an increase, with temperatures starting from 36.5°C.

The luteal phase (post-ovulation)

Duration: Approximately 14 days, but this may vary.

Basal Body Temperature : The temperature is generally higher during the luteal phase than during the other phases.

👉After ovulation, the released ovarian follicle transforms into what is called the corpus luteum, which produces progesterone. This hormone prepares the uterus for possible implantation of a fertilized egg. Progesterone has a thermogenic effect, meaning it increases the body's basal temperature. The temperature is generally between 36.7°C and 37.2°C.

How to follow your temperature curve?

Here are the steps to follow to create your temperature curve:

1) Take your basal temperature every morning:

Take your temperature before getting out of bed (the slightest movement can impact your temperature), preferably at the same time each day. Use a basal thermometer , which is more accurate for measuring small variations in body temperature. Favor taking rectal or vaginal temperatures (we know, it's not fun, but it's still more accurate). Comment if you took medication, drank alcohol or slept little, as this can also impact your temperature.

2) Note your temperature:

Record your temperature each day on a temperature curve graph . You can use a graph paper chart (already supplied with the Lady basal thermometer ) or a menstrual cycle tracking application like Clue which allows you to record your daily temperatures and save you the school supplies section of Monop' to find paper millimeter.

After several days, you may notice a slight drop in temperature followed by a rapid increase. This increase in temperature indicates that ovulation has occurred. In general, the temperature will increase by about 0.5 degrees Celsius.

3) Continue to take your temperature every day:

Continue to take your temperature every day for several months to establish a more complete temperature chart. This will help you determine your average menstrual cycle and identify temperature patterns that may indicate fertility problems.

Why use a basal thermometer and not a traditional thermometer?

Are you ready to rush to the pharmacy to buy a thermometer? Not so fast! You can't use just any thermometer to track your temperature curve. The basal thermometer is specially designed to accurately monitor small temperature variations related to the menstrual cycle. It is much more precise than a traditional thermometer. It can measure down to 0.01°C, ensuring stable and consistent readings, and it can store this data. Some models are also compatible with apps to help track and predict ovulation. For serious fertility monitoring, it is strongly recommended to use a basal thermometer rather than a standard thermometer!


What are its advantages and limitations?

When considering the basal temperature chart as a fertility tracking tool , it is essential to weigh both its benefits and limitations.

Advantages :

  • Non-invasive: One of the greatest strengths of this method is that it is non-invasive. No need for medical instruments or interventions; a simple thermometer is enough.
  • Inexpensive: With the exception of the initial purchase of a basal thermometer (specific for this use), there are no recurring costs associated with this method.
  • Educational: Regularly taking your temperature and monitoring its variations allows you to better understand your body and the menstrual cycle.

Limits :

Be aware that the temperature curve does not work for all people

and that it can be influenced by many factors, such as sleep changes, infections, stress, travel and medications. It is therefore important not to rely solely on this method to determine the time of ovulation, but rather to combine it with other methods of observing fertility signs, such as observing cervical mucus.

If you have a pregnancy plan, find all our natural solutions to help conceive a baby here.

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