Basal Body Temperature Charting: Predicting Ovulation, Pregnancy, & More

Many patients ask me about basal body temperature charting and whether they should chart when trying to conceive. Basal body temperature charting is one of the best tools to use when you are trying to conceive naturally. When combined with cervical fluid tracking, a BBT chart can help you time conception and determine whether you are ovulating or pregnant. The chart can also help you trouble shoot common issues related to your cycle and conception that many have gone unnoticed or undiagnosed.

When should I start a BBT Chart?

You can start a BBT chart at any point of your cycle, although most women like to start on the first day of their period. It’s a great exercise to try whether you are wondering when you ovulate or if you are trying to eliminate the guesswork while trying to conceive.

BBT charting is also one of the least invasive and least expensive methods to track your cycle (the cost is zero unless you need a new thermometer). I often recommend BBT charting to fertility clients so that they can determine a significant amount of information about their fertility before considering more involved testing.

How do I chart my BBT temperature?

To start a BBT chart, you’ll need a regular thermometer and a piece of graph paper. Yes, you can use a BBT thermometer, an excel spreadsheet, or cycle-tracking App but it is not necessary. Take your temperature at approximately the same time every morning and plot the points on your graph. You’ll create a pattern of temperatures in a relatively tight range before and after ovulation.

Day One of your cycle until ovulation is called the ovulatory phase of your menstrual cycle. After you ovulate, your temperature will rise 2/10 of a degree and remain at least 2/10’s of a degree higher than your last five pre-ovulatory temperatures. The day or two prior to this temperature shift is considered the best window to have intercourse. Watch for signs of fertile cervical fluid to help you determine peak fertility days.

Can a BBT chart reveal a short luteal phase?

The luteal phase of your cycle is the time after ovulation until you start your next period. A typical luteal phase is 12 to 16 days. If your luteal phase is less than 10 days, then this is considered to be a short luteal phase. Normal luteal phases allow enough time for egg implantation. This is one example of how a BBT chart may help you diagnose an issue related to conception.

Can a BBT chart tell me when I am pregnant?

Conversely, if your BBT chart shows 18 days or more of high temperatures-you’re pregnant! Many of my fertility clients prefer their BBT chart to tell them whether they are pregnant or not, once the novelty of taking multiple pregnancy tests wears off. Of course, at-home pregnancy tests can be taken much earlier than 18 days after ovulation.

What are the best BBT charting tips for beginners?

If you have never charted your basal body temperature, here are a few tips to get you started:

  1. Take your temperature for the length of your cycle, beginning day one of your menstrual period until the beginning of your next period. Take your temperature at the same time each morning.

  2. Take your temperature before you get out of bed, eat, move, talk, or use the bathroom.

  3. You must be sleeping for at least 3 hours to get an accurate temperature reading.

  4. Note that your temperature will rise every ½ hour as you sleep later.

  5. Heating pads, electric blankets, fevers, and drinking alcohol the night before will raise your temperature.

  6. Note on your chart if there is any reason that you think your temperature may not be accurate. This may help you decipher your chart at a later time.

  7. You can also note any cervical fluid observations or other symptoms on your BBT chart.

What are some other reasons to BBT chart?

Even if you're not trying to conceive, creating a BBT chart can help you tune into your body in a way that you haven't before. It may help you figure out cyclical patterns to other conditions such as headaches, constipation, insomnia, or anxiety. You can also use the same BBT chart to avoid pregnancy if you are not trying to conceive in any particular month. A health practitioner familiar with BBT charting can also help you analyze your cycle if your chart is difficult to interpret.

To learn more about all the benefits of BBT Charting, pick up a copy of Toni Weschler's book, Taking Charge of Your Fertility. This book is the best resource on the fertility awareness method, basal body temperature charting, cervical fluid tracking, and more. You can also visit the Taking Charge of Your Fertility website and use any smartphone recommended apps.

These smart phone apps are a great way to easily record your data or share information with a health care practitioner. Be aware that these apps often calculate “peak fertility days” based on a statistical average of your previous cycles. Try to ignore these calculations and pay attention to the real data in your chart.

It's hard to believe that so much information can be determined just by using a thermometer and a piece of paper. You will be amazed by everything you learn about your body and wonder why this wasn’t included in sex education class! For more ways to optimize your fertility naturally read our Natural Ways to Increase Cervical Fluid and Diet & Fertility articles.

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