Which influences change the body temperature and how they affect the female cycle

To ensure that all of the body’s processes run smoothly, the human body needs to maintain a certain temperature. However, this temperature is never completely constant. It is subject to fluctuations influenced by many factors. Here you can learn what affects your body temperature and how this impacts your fertility, for example.

What is core body temperature?

Core body temperature (CBT) refers to the temperature inside the human body and typically ranges between 36.5 and 37.4 °C in healthy adults, with an average of about 37 °C. In babies and toddlers, normal body temperature is slightly higher than in adults. In newborns, it is around 37.5 °C.

The core body temperature differs, for example, from the surface temperature (skin temperature) of the skin. Compared to the internal body temperature, it is subject to greater fluctuations and is much more dependent on external factors, such as extreme heat. In this case, the surface temperature can be significantly higher than the core body temperature.

Fluctuations in core body temperature are completely normal

This normal temperature can vary slightly from person to person. The measured temperature also depends on which body orifice is used for measurement, e.g., vaginal, oral, rectal, or axillary. The most accurate measurements can be taken vaginally or rectally. In addition, natural fluctuations must be taken into account. These are caused, for example, by the time of day, physical activity, and, in women, the different phases of the menstrual cycle. In women, core body temperature rises by approximately 0.3–0.5°C about 1 to 2 days after ovulation due to the thermogenic effect of progesterone.

Day-and-Night Rhythm – The Circadian Rhythm

It’s completely normal for your body temperature to fluctuate throughout the day (and night), and there’s no need to worry. At night, your core body temperature is lower than during the day. This is because you are not physically active while sleeping; your body rests and “conserves energy.” Due to various metabolic processes, your core body temperature is lowest in the second half of the night and then rises slightly even before you wake up. In the afternoon, it reaches its peak—at which point it can be up to one degree Celsius higher than in the early morning—and then drops again. The day-night temperature pattern resembles a sine curve and is also referred to as the circadian temperature rhythm.

When does the temperature reach its lowest point during the day?

Contrary to popular belief, the lowest temperature point (nadir) is not reached before getting out of bed; rather, research shows that it varies by up to three hours from person to person (Ekhart 2017). Scientists have thus demonstrated that the nadir is not a stable point in the circadian temperature rhythm.

Your core body temperature also drops slightly during a nap. In the daily view of your OvulaRing cycle chart, this is reflected by a brief, gentle drop in temperature and a gentle rise upon waking.

How does body temperature change throughout the night?

In the daily view of your OvulaRing cycle chart, your nighttime sleep is clearly indicated by the stair-step drop in temperature. Of course, this depends on how quickly you fall asleep. If you fall asleep quickly, the drop may be a bit steeper. If you have to get up during the night—perhaps because you’re woken by small children—you’ll see another small rise in temperature in the OvulaRing daily view of your cycle chart, though it won’t be as high as during the day. If you fall back asleep, your temperature will drop again. All of this can be tracked perfectly with OvulaRing.

Fever

Feverish illnesses, as shown in our featured image, are accompanied by an increase in core body temperature. At a core body temperature of 37.5–38.0°C, doctors refer to an elevated temperature (subfebrile temperature) in adults; at 38.1–39.4°C, they refer to a mild to moderate fever; and at 39.5–40.9°C, they refer to a very high fever. At temperatures above 41°C, a fever is life-threatening; the upper limit for survival is 44°C.

By the way, thanks to the high-resolution measurement of your core body temperature in your OvulaRing cycle chart, you can track exactly how high your fever actually is or was, and to what extent any fever-reducing medication you’ve taken is having an effect. You can recognize a fever pattern in the daily view of your OvulaRing cycle chart by the fact that your core body temperature often rises in a stair-step pattern and, after recovery, drops back to normal temperature days later in a stair-step or jagged pattern. When you view your entire cycle during a febrile illness, the temperature spike stands out quickly as a “temperature outlier,” resembling a sort of “jagged cone.”

How does a fever affect female fertility?

A feverish illness can your fertility temporarily affect it negatively, which can lead to a brief absence of ovulation or a shortened luteal phase until you have recovered. A fever puts a lot of strain on the body, so reproductive functions are temporarily “shut down” until you recover. With OvulaRing, you can track exactly how your body reacted to the fever and whether there was a ovulation whether or not ovulation occurred and when the cycle stabilized again after recovery. The accuracy and reliability of the OvulaRing are not affected by febrile illnesses.

Sports

Sports science has already shown that the human body’s temperature rises during intense physical activity. During a marathon, for example, core body temperature can rise to about 39°C—meaning it increases by up to 2°C in a short period of time! Conversely, however, an elevated body temperature is also a prerequisite for peak physical performance. Warming up beforehand improves various physiological processes and reduces the risk of injury.

How does exercise affect fertility?

In your OvulaRing cycle chart, you can identify temperature peaks following your workout by a very steep, sharp rise in temperature and a rapid, steep drop. This allows you to precisely monitor how much your body has heated up and cooled down again. If you’re trying to conceive, you should stick to moderate physical activity, as too much intense training can reduce your fertility. It has been shown that ovulation can be delayed or even stop entirely due to an excessive training load. Additionally, we’ve observed that high levels of physical exertion often lead to shortened second halves of the cycle … Take these warning signs seriously and avoid overtraining—especially if you’re trying to conceive. With OvuaRing, you can always track whether you’re (still) ovulating and have a a healthy second half of the cycle or whether your fertility is negatively affected by excessive exercise. The OvulaRing’s measurement accuracy and reliability remain consistent even during physical activity.

Sauna

When you’re in the sauna, your body temperature also rises rapidly to about 39°C. In air heated to between 60°C and 100°C, your body can only prevent its temperature from rising further for a short time by sweating profusely. For this reason, you should not exceed the recommended duration of a sauna session. By the way, using the sauna in a healthy way does not harm your fertility.

Alcohol consumption

Analysis of OvulaRing cycle charts has shown that a sharp drop in temperature can occur during sleep following a single instance of heavy alcohol consumption, such as after attending a party. In such cases, a brief drop in temperature to as low as 35.5°C has been observed.

Other influencing factors

Last but not least, other factors such as drug use, extreme heat, and extreme cold, as well as everyday physical activities like climbing stairs or carrying heavy groceries, stress, anxiety, and the use of certain medications (e.g., progesterone) can also affect your core body temperature.

With OvulaRing’s high-resolution, continuous core body temperature measurement, you can not only view your cycle curve and assess your individual cycle health—including your fertile window and ovulation timing—but also track even the slightest temperature fluctuations in your daily temperature readings. By the way, in your integrated OvulaRing cycle diary, you can accurately document whether you were sick, exercised, needed to take medication, and much more. This will help you later when interpreting temperature spikes.

Our team of OvulaRing experts is here to support you with your cycle chart analysis and provide detailed advice on your cycle health and any questions you may have. Find the OvulaRing package that’s right for you (including personalized cycle analyses): OvulaRing Shop.

References

Ekhart D et al. 2017. Dynamics of core body temperature cycles in longterm measurements under real life conditions in women. Chronobiology International. DOI: 10.1080/07420528.2017.1375942

Information from Pschyrembel online: Pschyrembel Fever

Temperature Regulation in Women: Effects of the Menstrual Cycle

OvulaRing Cycle Database