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Detecting Pregnancy or Ovulation on Your Basal Body Temperature Chart

What is a Basal Body Temperature Chart

Detecting pregnancy or ovulation is likely the reason you started using a basal body temperature chart in the first place. Am I right?

If you're trying to achieve or avoid pregnancy then your charts will give you the data you need to detect pregnancy or ovulation.

Let's start by discussing the importance and basics of charting your basal body temperature (BBT) and giving you a great foundation for understanding your charts!

Importance of Charting Your BBT

In the book, The Fifth Vital Sign, Fertility Awareness Educator Lisa Hendrickson-Jack affirms that "your menstrual cycle is a vital sign, just like your pulse, temperature, respiration rate, and blood pressure."

That's because your fascinating cycle can tell you a lot about your overall health.

One of the unbiased fertility signs you can track is your basal body temperature. 

By taking note of your BBT and observing trends throughout the menstrual cycle you can:

  • Track ovulation
  • Detect pregnancy
  • Avoid pregnancy
  • Recognize and troubleshoot hormonal and other issues

Basics of Charting Your Fertility Indicators

In order to get a clear understanding of when you are ovulating or pregnant, you will need to chart your basal body temperature daily. You might also consider charting cervical mucus.

The basics of getting started include:

First, you'll begin observing how your body changes throughout your menstrual cycle by taking note of your basal body temperature when you first wake up each morning. 

Using a wearable fertility tracker like Tempdrop will make identifying your most accurate BBT seamless!

Next, you need to document your basal body temperature on your BBT chart. Connecting the dots between each temperature on your printable paper-pencil chart. Or plugging the data into a high-quality app like OvuView.

Once you have a few months worth of data to review you will begin to notice patterns and trends. This info will ultimately help you understand your ovulation time and help you detect pregnancy.

Now that we understand the basics we can begin exploring how to detect ovulation when using your BBT chart.

Detecting Ovulation Using Your Basal Body Temperature Chart

Unfortunately, you can't foresee in advance ovulation by tracking your BBT but you can confirm that it has happened!

Once you have 2 or more months of charts to review, predicting ovulation for your next cycle will become easier because you'll begin to notice which day of your cycle is your ovulation day based on your thermal shift. 

Thermal Shift Patterns

When glancing at your BBT chart you will see a spike in temp 1-2 days after ovulation. This is an indicator of your bodies thermal shift from pre-ovulation phase to the post-ovulation phase. For most women, ovulation occurs around day 14.

However, relying on this is the reason why the rhythm method has given fertility awareness methods such a bad name! Understanding common thermal shift patterns is key to properly identifying ovulation each month, no matter which cycle day it falls on.

The most common pattern is the standard thermal shift. Other thermal shift patterns include slow-rise, stair-step rise and fall-back rise. Let's chat about each one briefly.

Standard Thermal Shift

If you notice a series of low temps and then an obvious "shift of at least two-tenths of a degree, followed by a consistent range of high temps that remain high until the end of that cycle (Weschler, 2015)" this is evidence that ovulation has occurred.

If you're one of the lucky ducks who experiences a standard thermal shift pattern then you will likely find it easy to interpret your charts.

basal body temperature chart

Other Thermal Shift Patterns

Many women will observe a thermal shift pattern that doesn't fit the description above.

The Slow-rise will look like a series of slight increases in comparison to the six temps before it as you can see on the chart below. For standard length cycles, the increases may start around day 14.

basal body temperature chart

If you observe temps that rise for 3 days around Day 14 for cycles of standard length and then increase again around Day 17 you are observing the stair-step rise. You can see how the temps rise in small groups of 4 or 5 that mimic stair steps on the chart below. 

Example of staircase rise

Some women will note a pattern called the fall-back rise in which your temps will rise around Day 17 (again, in standard length cycles) and then fall back, only to rise above the coverline again on the days that follow. The two charts below reflect the fall-back rise.

fall-back rise

fall-back rise

The thermal shift patterns mentioned above happen as a surge of estrogen hits your system prompting your body to ovulate.

If you are trying to conceive you'll want to consider having intercourse 2 or 3 days before you ovulate. 

Once you identify ovulation the two-week wait begins if you are TTC.

How to Detect Pregnancy Using Your BBT Chart

Detecting pregnancy is fairly simple when reviewing your basal body temperature chart.

As we previously discussed, your temps will rise 1-2 days after ovulation. Then if you're pregnant, you'll notice that your temps stay elevated and don't drop off with menstruation.

Taking a home pregnancy test can confirm a pregnancy 9+ days post ovulation.

Using Your BBT Chart to Detect Ovulation or Pregnancy

To wrap things up, here's the quick and dirty version of detecting pregnancy or ovulation on your basal body temperature chart.

At first, your temps will be lower. Mid-cycle you’ll notice a rise in your basal body temperature.

The temps will stay high until they drop again. Basically, once your temps rise up for at least 3 days and stay elevated, you'll know you've ovulated. If your temp stays up beyond 16 days then you're probably pregnant.

If you'd like to learn more about FABM, including how to chart your cycle, identify your fertility window, and be your own ovulation calendar, download Tempdrop's free Introduction to Fertility Awareness, a beautifully-designed guide written by seven certified educators.




Weschler, T. (2015). Taking Charge of Your Fertility (20th Anniversary ed.). New York, NY: HarperCollins.