What is Basal Body Temperature?


A person's Basal Body Temperature (BBT) is the lowest body temperature the body will reach in the course of a twenty-four hour period, which typically occurs while a person is sleeping.

Measuring BBT is done immediately upon awakening, before one carries out any physical activities that might raise one's body temperature.

BBT is an issue in conception and fertility because ovulation tends to raise the basal body temperature of a woman's body between one-half and one full degree Fahrenheit (or one quarter to one half degree Celsius). This fact makes it possible for a woman to monitor her fertility. This is known as a biphasic pattern.

A monthly menstrual cycle features the activity of a pair of hormones. During the cycle's first half, the so-called follicular phase, the hormone estrogen aides the ovaries in producing an egg that will be released during ovulation. During the cycle's latter half, the so-called luteal phase, progesterone dominates

Before ovulation, when estrogen is at work in the cycle, a woman's body temperature will be slightly lower than it is following ovulation, when progesterone becomes the dominant hormone. When monitoring one's basal body temperature, an increase in the temperature (when charted over time) would be indicative of ovulation.

You can download useful basal body temperature charts here.


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