Chart your Basal Body Temperature and predict ovulation - your most fertile time of the month for conceiving a baby - with a specially designed digital BBT Thermometer. When a woman ovulates, a rise in body temperature takes place in order to provide a more fertile environment for conception. By monitoring when this temperature change occurs, you can determine when ovulation takes place in your cycle. Recording each day's basal body temperature with a BBT Thermometer will help you predict ovulation. The Fairhaven Health Digital Basal Thermometer provides temperature readings to 1/100th of a degree - perfect for fertility charting and predicting ovulation.