Labels:text | font | screenshot | book | number | document OCR: BASAL BODY TEMPERATURE T THE TEMPERATURE of the body at rest, known as the basal body temperature (BBT), can be used to detect a woman's fertile phase. It should be taken at the same time every day, preferably with a special fertility thermometer. When you record a temperature for three days in a row that is higher than on all of the previous six days, the fertile time is over. The difference is about 0.4º-0.8ºF (0.2"-0.4℃).