The basal temperature in pregnancy

The basal temperature in pregnancy

Low body temperature (hypothermia)

If your only symptom is a low body temperature, this is not a cause for concern. If low body temperature occurs along with other symptoms, such as chills, tremors, breathing problems, or confusion, this may be a sign of a more severe illness.

Low body temperature often occurs as a result of exposure to cold. But it can also be caused by alcohol or drug use, shock, or certain conditions such as diabetes or hypothyroidism.

A low body temperature can also occur in case of infection. This is more common in newborns, older adults, or weak people. A severe infection, such as septicemia, can also lead to an abnormally low body temperature.
High body temperature (heatstroke)

Heatstroke happens when the body cannot control its temperature, and the body temperature continues to rise. Symptoms of heatstroke include mental disturbances (such as confusion, delirium, or loss of consciousness) and redness, warmth, and dryness of the skin, even under the armpits.

Heatstroke can be fatal. It requires emergency medical treatment. It causes severe dehydration and can cause body organs to stop working.

There are two types of heatstroke.

Classic heatstroke can occur even when a person is not active, as long as it is hot and the body cannot cool itself enough through sweating. The person may even stop sweating. Classic heatstroke can develop over several days. Babies, older adults, and people with chronic health problems are at the highest risk for this type of heatstroke.
Exercise-induced heatstroke can occur when a person is working or exercising in a hot place. The person may sweat a lot, but the body generates more heat than it can eliminate. This causes the temperature to rise to high levels.
What is the basal temperature?

The basal temperature is when the body reaches rest, typically after having slept a minimum of 5 or 6 hours. Therefore, to know it, you must measure it when you wake up.
The basal temperature during menstruation

The basal temperature in women varies with the menstrual cycle, lower from the end of the period until ovulation. This makes it a valuable indicator of fertility and is also used as a natural contraceptive method.

After ovulation, due to the increased presence of the hormone progesterone, the temperature rises slightly, about 0.3-0.5 degrees. When this elevation is maintained for three days in a row, it indicates that the fertile period has ended. The temperature will drop again after the following rule.

How to take your basal temperature

It begins on the first day of menstruation.
Measure the temperature before getting up and after having slept at least 5 hours.
Always measure at the same time and on an empty stomach.
Choose the oral, anal, or vaginal determination and do it always in the same way.


Place the tip of the thermometer under your tongue and keep your lips closed.

Insert the thermometer into the vagina.

Use petroleum jelly or lubricant and insert the thermometer’s tip into your rectum while holding the fetal position.
What thermometer do I use to measure basal temperature?

You can use any thermometer to measure your basal temperature, if possible, that allows you to obtain an accuracy of up to one-tenth. There are basal thermometers on the market that are more accurate than normal ones. This is important given the slight variations that we are going to detect.

It is not recommended to place the thermometer in the armpit, as the results may be inaccurate. It is essential not to move during the process because this could raise your body temperature slightly.

How long you need to hold the thermometer for the correct intake varies depending on the type of thermometer. Digital ones are faster than glass ones. When the result of the thermometer is between two marks, it is advisable to write down the smaller number.
Factors that can alter the basal temperature

The increase in ovulation does not always occur. In addition, several factors modify the basal temperature, altering the results, for example:

Sleeping less than 4 hours.
Drink alcohol.
Some drugs
A cold.
A copious dinner.

Therefore, this is not an infallible system to detect or rule out fertile days, especially if you do not have regular cycles. Approximately 24% of women who use this procedure for birth control will become pregnant within a year. Therefore, whether you want to get pregnant, as if you want to avoid it, we recommend using additional, more reliable methods.

The basal temperature in pregnancy

During pregnancy, the basal temperature is not stable either.

At the beginning and until week 10, it is usually higher than usual. This rise is also due to the increase in progesterone in this period. It reaches very high levels at the beginning and falls from week 11.

If you observe that the increase is maintained beyond 18-20 days in the temperature registry, likely, you are already pregnant. If this happens to you, do not hesitate to take a pregnancy test or go to your doctor to confirm if you are expecting a baby.

The basal temperature method, based on fertility awareness, is a type of natural family planning. Basal temperature is your body temperature when you are totally at rest. Ovulation can cause a slight increase in basal temperature.

You will be most fertile in the two to three days before the temperature rises. By tracking your basal temperature every day, you can predict when you will ovulate. This can help determine when you are most likely to conceive a child.

If you want to get pregnant, you can use the basal temperature method to determine the best days to have sex. Similarly, if you don’t want to get pregnant, you can use the basal temperature method to determine which days you shouldn’t have unprotected sex.

Using the basal temperature method alone may not allow enough time to prevent pregnancy effectively. People often use this method in combination with other fertility awareness-based methods to prevent pregnancy.

Why it should be done

Basal temperature can be used as a way to predict fertility or as part of a contraceptive method, helping you determine the optimal days to have or avoid unprotected sex.

Keeping a basal body temperature to predict fertility or contraception is inexpensive and has no side effects. Some women may decide to use the basal temperature method for religious reasons.

The basal temperature method can also be used to detect pregnancy. After ovulation, an increase in basal temperature that lasts 18 days or more can be an early indicator of pregnancy.

The basal temperature method is often combined with the cervical mucus method for natural family planning, in which you keep track of cervical secretions during the menstrual cycle. You can also use an electronic fertility monitor to measure hormone levels in your urine, indicating which days you are fertile. This combination of approaches is sometimes referred to as the symptothermal or syntohormonal method.