Basal Body Temperature Method
Another way of estimating high-fertility days is through temperature, using the basal body temperature method. Immediately before ovulation the basal body temperature (BBT, the body temperature in the resting state on waking in the morning) drops slightly. After ovulation the corpus luteum releases more progesterone, which causes the body temperature to rise slightly (0.2°F). Because these temperature changes are slight, a thermometer with easy-to-read gradations must be used. Special electronic thermometers have been developed for measuring BBT and are effective in indicating fertile times in the cycle.
Female sterilization accomplished by severing or tying the fallopian tubes.