Definitions for "Basal body temperature chart"
An inexpensive way of detecting ovulation through the effect progesterone has on the hypothalamus, increasing the body's temperature a few tenths of a degree. Best recorded using a BBT thermometer (with a smaller scale than thermometers used to record fevers or high temperatures) first thing in the morning before rising, and preferably in the vagina for accuracy. Day 1 of the chart is the first morning when there is menstruation (a period). Commonly there's a dip in the temperature just before the sustained rise that indicates that ovulation has occurred (a "biphasic chart"). The chart typically records the days you are menstruating, when you have sex and when you're aware of mucus and ovulation pain. Best used to document: (1) the presence and length of the luteal phase, especially if clomiphene is being used for ovulation induction; and (2) the timing of symptoms such as premenstrual spotting. Not as good for predicting ovulation as LH-testing in urine.
A woman measures her oral temperature each morning upon awakening. With ovulation, temperature rises approximately one half degree during the second half of the menstrual cycle (biphasic pattern).
A daily body temperature chart that provides a rough idea of when ovulation occurred. This is possible because body temperature rises when the corpus luteum produces progesterone (after ovulation) and drops at or just before the beginning of menstruation, when estrogen and progesterone levels fall (see also biphasic pattern of temperature on BBT chart).