A woman’s hormones cause her body’s basal temperature to fluctuate before and after ovulation. Charting a woman’s basal body temperature is an inexpensive method for predicting her fertile times and has no side effects. Couples may use the basal body chart as a natural birth control method for religious reasons. Infertility specialists may often recommend this as part of infertility testing and, in some cases, the basal body temperature chart may be an early indicator that pregnancy has occurred.
Basal Body Temperature
The basal body temperature is the body’s temperature when fully at rest, according to the Mayo Clinic. When a woman ovulates, her basal body temperature will rise slightly. It will remain elevated for 10 to 14 days after ovulation, then drop and the menstrual period will begin.
Using the Thermometer
Available in either glass or digital models, a basal body thermometer is used orally and measures in increments of 10th of a degree. A woman uses it immediately upon waking, before getting out of bed or drinking anything. It is best if the basal body temperature is taken at the same time each day. The woman places the thermometer under her tongue and lies still. It is left in place for 5 minutes if it is a glass thermometer, or it signals when it is a digital thermometer. If the glass thermometer registers between two marks, the lower number is used.
Charting the Basal Body Temperature
Record the basal body temperature on a chart. Note things that occurred which might affect the temperature, such as illness, stress, interrupted sleep, travel, medications or consumption of alcohol on the previous day. After several months, a pattern will emerge which can be used to determine optimum fertility.
Temperature and Pregnancy
When conception occurs, a woman’s basal body temperature will not drop, but it will remain elevated. If nothing has occurred that might alter the woman’s temperature, an elevated basal body temperature for 18 or more days may be one of the first signs that a woman is pregnant.
