If you're trying to get pregnant, it's helpful to know exactly when you ovulate so you can time sex accordingly. Many women have had success using ovulation predictor kits, which are handy because they tip you off before you ovulate. Others prefer to track their ovulation cycle by charting their basal body temperature (BBT) and monitoring their cervical mucus (CM).

What is basal body temperature?

Your basal body temperature (BBT) is your lowest body temperature in a 24-hour period. To get an accurate reading, you must take your temperature when you first wake up in the morning, before you even sit up in bed.  And you'll need to use a basal thermometer, which is sensitive enough to measure minute changes in body temperature. Try to wake up and take a reading at about the same time each morning.

Basal thermometers are available at most drugstores and usually come with a chart for recording your temperature each day. BabyCenter also has a blank chart you can print out, along with step-by-step instructions on how to use it and a prefilled sample chart. You'll probably want a few copies of the blank chart because it will take a few cycles to figure out your ovulation pattern. (There are also apps you can use.)


Ovulation Calculator


Before ovulation, your BBT probably ranges from 97.2 to about 97.7 degrees Fahrenheit. But two or three days after you ovulate, hormonal changes cause a rise of 0.4 to 1.0 degree in your BBT, which lasts at least until your next period. (You may notice your temperature spiking on other days here and there, but unless it stays up, you probably haven't ovulated yet.) If you become pregnant, your temperature will stay elevated throughout your pregnancy.

Of course, since a BBT chart will only tell you that you've already ovulated, the first month of recording your temperature won't be very helpful. But by charting your BBT for a few months, you'll be able to see whether there's a pattern to your cycle, which may enable you to predict ovulation the next time around – as well as the best days to have sex (or be inseminated) if you want to get pregnant.

Keep in mind that if you're sick or don't take your temperature immediately after waking up, any pattern that you find may be inaccurate.

In addition to helping you predict the day of ovulation, BBT charts can also help your doctor pinpoint the cause of any infertility issues. If certain phases of your cycle are short, you may have a hormonal imbalance, for example.