Widely unknown, basal temperature is one of the indicators that can help determine when you ovulate, and therefore optimize your chances of getting pregnant. What is it for ? How do we measure it? When ? Aufeminin explains everything to you.
The word "basal" might sound a bit strange if you don't know what it is, yet you don't have to look far. Basal temperature represents the lowest temperature the body reaches while at rest. Therefore, the one you have when you wake up, before starting an activity. It is observed carefully when one wishes to become pregnant, since its increase allows determine the ovulation period more or less accurately, and therefore know when fertility is highest.
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Indeed, its sudden increase at the time of ovulation is one of the symptoms that can alert. This is caused by progesterone, the hormone the body produces in the luteal phase to help the fertilized egg nest in the lining of the uterus. During the first phase of the cycle (the period from the first day of menstruation to ovulation), your basal temperature is stable and usually below 37 ° C. It drops a few tenths just before ovulation to increase and exceed 37 ° C when it begins.
Read also: The temperature curve for getting pregnant: how does it work?
How to measure your basal temperature?
Conventional mercury thermometers, used to measure fever, do not offer the ability to take basal temperature accurately. For this, a specific thermometer is necessary, because it has notches of values more distant from each other and therefore allows to record even the smallest variations.
Know that it is very important to measure your basal temperature after at least three hours of rest. It is even best to take it after at least six hours of sleep, before getting up and getting out of bed. It is also important to always measure it at the same time (preferably in the morning), on a regular basis and by noting on a graph the temperatures recorded day after day.
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Basal temperature can be measured in three ways: orally, vaginally or rectally. Choose from the three methods and keep the same for the entire measurement period. Note that the rectal route is considered to be the most accurate, while the oral route the least reliable, due to possible falsification of the values if you sleep with your mouth open.
How do you relate basal temperature to ovulation?
If monitoring your basal temperature is for the purpose of getting pregnant and determining your exact ovulation date, use this method below.
Start measuring your basal temperature from the fifth day after the start of your cycle, and then measure it every day until the start of your next cycle. It is important to be regular in the measurements.
To calculate your ovulation date, it's here.
Record your temperatures to tenths of a degree day by day on a graph, which will allow you to observe the changes over the days. How to build the graph? It's very simple. Enter the temperatures that you see day by day on the vertical axis of the graph, and the days of the month on the horizontal axis.
How to read the basal temperature graph?
As the days go by, you will see changes in the trend of the chart line. During the first phase of ovulation (follicular phase), you will notice that the temperature will tend to fall on average, until it drops for only one day.
Thereafter, it will rise above average, which means you are in the lutein phase of the cycle. This phase involves the creation of the corpus luteum, a gland responsible for the production of hormones, which are useful in event of conception. The fall and the rise which follows correspond precisely to ovulation. It is formally confirmed if the rise in this basal temperature is observed for at least three consecutive days.
The temperature curve for getting pregnant: how does it work?
However, it may happen that the rise in temperature does not occur immediately after ovulation, but after two or three days. Either way, this is a great time to have sex because you are more fertile. After ovulation ends, your basal temperature stays high until a few days before your next period, when it drops again. According to women, the temperature drops on the day of their period, or even the next day.
Other symptoms of ovulation to watch out for
When measuring basal temperature and graphing, it is also important to observe the appearance of cervical mucus, which emerges from the vagina. This is naturally produced by the body to defend the uterus and marks, thanks to the change in its texture, the initial and final phases of ovulation. When the mucus appears stringy and watery, almost transparent, to the point that you can stretch it several inches between your thumb and forefinger, it means you are in the preovulatory phase.
Read also: Painful ovulation: is it normal to have pain when I ovulate?
During this phase, the amount of estrogen in the blood, which is the female hormones responsible for regulating the ovarian cycle, increases. Then comes the second hormone of the ovarian cycle, progesterone. As the amount increases and estrogen decreases, cervical mucus also changes in appearance, becoming more lumpy and yellowish. On the day of ovulation, the texture of cervical mucus is comparable to that of an egg white: fluid, elastic, shiny and transparent, it is also more abundant.
Basal temperature: values and exceptions
In a so-called "normal" representation, the basal temperature measurements should show a two-phase pattern, that is, two distinctly different phases, one with a lower temperature and then an increase. During the preovulatory phase, basal temperature reference values are between 36.3 ° and 36.7 °. When ovulation is in progress, the values to be expected are higher: 37 ° or even a few tenths of a degree more.
But, with every woman and cycle being different, there are cases when the course is not biphasic, which can lead to several exceptions. It is possible that an anovulatory cycle has occurred, in other words without ovulation. In this specific case, the temperature remains constant throughout the cycle, or causes a "roller coaster", without noticing the increase in basal temperature typical of the two-phase cycle. The cycle without ovulation can be caused by hormonal imbalances, a topic you should discuss with your gynecologist if this happens often.
There are other causes that can interfere with the detection of an increase in basal temperature:
- Medication
- Fever
- Less than 4 consecutive hours of sleep
- Alcohol or drug use
- Vaginitis (in case of vaginal measurements)
- The Depression
- Anxiety
There are many variables that can affect the reliability of the measurement, so it is always a good idea to compare your results with your gynecologist, especially if you have decided to get pregnant.