Basal Body Temperature

Whether you are trying to prevent or achieve pregnancy, charting your cycle can help. As you go through your menstrual cycle, your body gives you indications about when you are ovulating.

Why Chart Your Menstrual Cycle?

Charting your menstrual cycle may help you become pregnant more quickly by giving you a fertile window that is unique to your body. If you are trying to conceive but have been unsuccessful, your chart can be shared with a fertility doctor, if needed. Charting your cycle may also help you avoid unwanted pregnancy by knowing when to practice abstinence or use contraceptives during your fertile window.

Taking Your Basal Body Temperature

Your basal body temperature (BBT) changes throughout the month according to where you are in your cycle. Tracking your BBT helps you determine when you are most fertile. Factors include:

  • Before ovulation, your BBT is usually about 96 F (35.55 C) to 98 F (36.66 C).
  • During ovulation, your body releases the hormone progesterone. This raises your BBT by 0.4 to 0.8 F degrees a day or two after ovulation.
  • During ovulation, your body releases the hormone progesterone. This raises your BBT by 0.4 to 0.8 F degrees a day or two after ovulation.
  • This rise in temperature usually lasts until your period starts.
  • If you become pregnant, your temperature will stay elevated during your pregnancy. After charting for a couple of months, you may see a pattern emerge.
  • You’re most fertile 3-4 days before ovulation, and 12 to 24 hours after ovulating.

Please note that although BBT charting is widely used, it’s not 100% accurate. Some women may not see a clear pattern. You may ovulate at different times in your cycle from one month to the next, which can make it difficult to predict.

Basal Body Temperature Accuracy

To help in this process, we suggest using a basal body thermometer. You can find them at most pharmacies or view our Products page for more information. Here are some tips to help you get an accurate reading for your basal body temperature:

  • Keep the thermometer by your bedside.
  • Take your temperature the same time every morning while still in bed.
  • Don’t do anything before measuring your BBT. Don’t eat, drink, smoke, get up, or move around.
  • You can take your temperature orally, rectally, or vaginally. Be consistent and do it the same way every time.

Have your doctor help you interpret your chart. Charts vary widely from one woman to the next. Click here to view sample completed charts.

Cervical Fluid

The fluid produced by your cervix changes at certain times during your cycle. You can help predict ovulation by tracking these changes. Using this and BBT together may be more effective than using just one method. However, this is not a fool proof method. Fluid released by the cervix serves different purposes.

  • It prevents sperm from getting into the uterus when you aren’t ovulating.
  • It protects sperm and helps it along on its journey toward the egg when you are ovulating.

An example of a typical pattern of cervical fluid changes for a woman with a 28-day cycle:

  • Days 1-5: Your period starts.
  • Days 6-9: Vagina is dry with little to no fluid.
  • Days 10-12: Sticky, thick fluid appears, gradually becoming thinner and whiter.
  • Days 13-15: Fluid becomes thin, slippery, stretchy, and clear. This is the most fertile stage.
  • Days 16-21: Fluid becomes sticky and thick again.
  • Days 22-28: Vagina secretions dry.

If you do not detect any fluid, you can check multiple times a day. Some women produce little to no fluid while others may produce an abundance of fluid. With clean hands, swipe 2 fingers over the opening of your vagina. You should be able to see your cervical fluid. Rub the 2 fingers together and pull apart to see the consistency.