Basal body temperature is the body temperature measured immediately after awakening and before any physical activity has been undertaken. In women, ovulation causes an increase of one-half to one degree Fahrenheit (one-quarter to one-half degree Celsius) in basal body temperature (BBT); monitoring of BBTs is one way of estimating the day of ovulation. The tendency of a woman to have lower temperatures before ovulation, and higher temperatures afterwards, is known as a biphasic pattern. Charting of this pattern may be used as a component of fertility awareness.
If pregnancy does not occur, the disintegration of the corpus luteum causes a drop in BBTs that roughly coincides with the onset of the next menstruation. If pregnancy does occur, the corpus luteum continues to function (and maintain high BBTs) for the first trimester of the pregnancy. After the first trimester, the woman's body temperature drops to her pre-ovulatory normal as the placenta takes over functions previously performed by the corpus luteum.
Very rarely, the corpus luteum may form a cyst. A corpus luteum cyst will cause BBTs to stay elevated and prevent menstruation from occurring until it resolves, which could take weeks or months.
Pregnancy tests are not accurate until 1-2 weeks after ovulation. Knowing an estimated date of ovulation can prevent a woman from getting false negative results due to testing too early. Also, 18 consecutive days of elevated temperatures means a woman is almost certainly pregnant.
Tracking basal body temperatures are a more accurate method of estimating gestational age than tracking menstrual periods.
US Patent Issued to Cambridge Temperature Concepts on Sept. 24 for "System and Method for Estimating a Basal Body Temperature and Forming an Indication of Ovulation" (British Inventor)
Sep 24, 2013; ALEXANDRIA, Va., Sept. 24 -- United States Patent no. 8,540,644, issued on Sept. 24, was assigned to Cambridge Temperature...