Temperature and ovulation: the thermometer of your fertility

The human body, with its complexity and subtleties, has an incredible ability to give us clues about its inner workings. Among these clues, measuring basal body temperature during ovulation proves to be a valuable indicator, particularly for menstruating people who want to understand the rhythms of their fertility. Want to learn more about BBT ? Want to know how to track 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, usually 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.

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Measuring your temperature curve: a method for predicting ovulation

The temperature chart isn't just a medical concept or a biological phenomenon. It's a valuable tool for many menstruating people who want to better understand their bodies. There are several reasons why people might adopt this practice. Let's explore the different reasons why this chart is a key element of the menstrual cycle.

Know your ovulation phase

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 a certain precision the moment of ovulation . After all, it's a bit like having a natural GPS for our fertility! Namely, 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 the case of pregnancy, the basal body temperature remains above 37°C for at least 10 to 14 days, until the next menstrual period is due.

Read: How to calculate your ovulation date >

Know your fertility window

Whether you're planning to expand your family or, on the contrary, prevent pregnancy, tracking your temperature curve is a natural way to better understand your fertility window. Of course, used alone, it's not a substitute for medical contraception, but it provides invaluable insight into your most fertile days.

Read: What are the most dangerous days when a woman's risk of getting pregnant is highest? >

But it is also an anomaly detector

Far beyond simply detecting ovulation, this curve can also be a warning signal. A lack of temperature rise? This could indicate a cycle without ovulation. Other irregularities could also be valuable clues about reproductive health.

Basal temperatures during the 4 phases of the menstrual cycle

The bodies of people with vulvas are a marvel, regulated by natural rhythms and hormonal fluctuations that directly influence basal body temperature. Understanding these thermal fluctuations in relation to the four phases of the menstrual cycle can provide profound insight into reproductive health and the timing of ovulation. Shall we take a closer look at all of this?

The menstrual phase (period)

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

Basal Body Temperature: During this phase, the temperature is usually 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.

👉 Your period marks the beginning of a new cycle. During this time, your body sheds unused uterine lining. Hormone levels, particularly estrogen and progesterone, are relatively low, resulting in a lower basal temperature.

Basal temperature during the follicular phase (pre-ovulation)

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

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

👉 This is the phase before ovulation. Estrogen begins to rise, stimulating the growth of ovarian follicles containing eggs. Although estrogen is rising, it does not significantly affect BBT until ovulation approaches. BBT is typically between 36.1°C and 36.7°C.

Basal temperature during ovulation

Duration: Very short, usually 24 to 48 hours.

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

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

Basal temperature during the luteal phase (post-ovulation)

Duration: Approximately 14 days, but may vary.

Basal Body Temperature : Temperature is generally higher during the luteal phase than during 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 basal body temperature. The temperature is usually between 36.7°C and 37.2°C.

Basal temperatures during conception

Do you think you've gotten pregnant and want to check it out using your basal temperature? There's nothing better than taking a pregnancy test and having a blood test! However, monitoring your basal temperature can give you some insight.

Basal temperature during fertilization

During fertilization, a woman's basal temperature remains as high as after ovulation . There is no significant temperature change specific to fertilization itself. Typically, after ovulation, basal temperature increases by 0.3 to 0.6 °C, reaching around 36.5 °C to 37.0 °C.

Basal temperature during implantation

Some women may experience a slight temporary drop in temperature, called an implantation dip, approximately 7 to 10 days after ovulation, corresponding to the implantation of the embryo in the uterus. However, this drop is not systematic and is not observed in all women. In general, the temperature during implantation therefore remains around 36.5 °C to 37.0 °C during this period.

Basal temperature during pregnancy

In pregnancy, the basal temperature during pregnancy is between 36.5 °C and 37.0 °C . In fact, after ovulation, the temperature does not change further. This continuous rise is due to the sustained production of progesterone by the corpus luteum and then by the placenta. If a woman observes that her basal temperature remains elevated for 18 consecutive days or more after ovulation, this may be an early sign of pregnancy.

How to monitor your basal temperature curve?

Did you know that tracking your temperature curve is part of symptothermal method , which is a method of observing the cycle? Here are the steps to follow to create your temperature curve:

1) How to take your basal temperature?

Take your temperature before getting out of bed (even the slightest movement can affect your temperature), preferably at the same time each day. Use a basal thermometer , which is more accurate for measuring small changes in body temperature. Instead, take your temperature rectally or vaginally (we know, it's not fun, but it's still more accurate). Comment on any medications you've taken, alcohol you've been drinking, or poor sleep, as these can also affect your temperature.

2) Note your temperature:

Record your temperature each day on a temperature curve chart . You can use a graph paper chart (already included with the Lady basal thermometer ) or a menstrual cycle tracking app like Clue that allows you to record your daily temperatures and save you the hassle of searching for graph paper in the school supply aisle at Monop.

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. Typically, your temperature will increase by about 0.5 degrees Celsius.

3) Continue to take your temperature every day:

Continue taking your temperature daily 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 classic thermometer?

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 fluctuations related to the menstrual cycle. It's much more accurate 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's highly recommended to use a basal thermometer over a standard thermometer!

Learn more about the thermometer

What are its advantages and limitations?

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

The advantages:

• Non-invasive: One of the greatest strengths of this method is that it is non-invasive. No medical instruments or procedures are required; a simple thermometer is sufficient.
• Inexpensive: Except for 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.

The limits:

Be aware that the temperature curve does not work for everyone.

and that it can be influenced by many factors, such as changes in sleep patterns, 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 signs of fertility, such as observing cervical mucus.

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