Digital Basal Thermometer is one of the most commonly used ways to track fertility. It is a simple method and very inexpensive. A digital basal thermometer is less than $10 (for a good, sensitive one at Beyond Fertility Shop).
The importance of using a digital basal thermometer as opposed to a regular temperature taking thermometer is that the digital thermometer takes your basal temperature. Basal temperatures are about 1 degree lower than with a normal thermometer. They are sensitive to your resting temperatures.
A digital basal thermometer does not take a rocket scientist to decipher. It is very simple. Just wake up and grab the thermometer from next to the bed and place beneath your tongue. Wait until it beeps and record the temperature on your chart or even just keep track of the numbers.
You will begin to notice a pattern. In the first week of your cycle you should see numbers that are around mid-97s. Just before ovulation, if your cycle is going well and hormones are balanced, you will see a sudden dip which signals that estrogen has spiked and then a sudden rise the next day. This is an indication that ovulation has occurred. At this point your progesterone should begin to dominant the cycle and cause your temperatures to rise.
If pregnancy occurs then most women will see a second rise in temperatures at about 5-8 days after ovulation. This is a good sign that pregnancy has taken place and your temperatures will stay high, if all is well, until it is time to deliver.
Please note that this is just a simple explanation and more information can be found on our site under Fertility Charting on how to do this method. See other methods as well, including Fertility Tracker, how to check cervical position or even the OvaCue Monitor.