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Triphasic Body Basal Temperature Charting and Pregnancy

Can a Triphasic BBT Chart Be an Early Sign of Pregnancy?


Updated July 10, 2014

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In fertility charting circles, there is a coveted body basal temperature chart pattern known as a triphasic chart. Many women, including myself, scan their BBT charts each month in search of early pregnancy signs. What is a triphasic chart? And is a triphasic chart a reliable early pregnancy sign?

What Is a Triphasic BBT Chart?

Every BBT chart that indicates ovulation shows a biphasic pattern. Biphasic, when it comes to BBT charting, just means that there is a clear, sustained upward temperature shift at the time of ovulation, making a clear distinction between the temperatures that came before ovulation, and the temperatures that came after ovulation. For more information on the basics of BBT charting, read this step-by-step piece on how to chart your body basal temperature and how to detect ovulation with a BBT chart.

With a triphasic BBT chart pattern, there is a third, sustained upward shift in temperature, usually occurring around 9 days post-ovulation.

Since progesterone is the hormone that causes the upward shift in temperature at ovulation, the theory is that increased progesterone from pregnancy might cause another upward shift in temperature.

Is a Triphasic Chart a Reliable Early Pregnancy Sign?

FertilityFriend.com, a free fertility charting online software company, did an informal analysis of the BBT charts on their site, to see if a triphasic pattern might indicate pregnancy. This was by no means a scientific study, but the results are still interesting to consider.

In their informal analysis, they considered a triphasic pattern to be a second, significant upward shift in temperature of at least 0.3 F, occurring at least 7 days after ovulation.

After analyzing almost 150,000 BBT charts, they found that 12% of all pregnancy charts showed a triphasic pattern. When looking at non-pregnancy charts, they found that only 5% of charts showed a triphasic pattern. So, based on this data, you have about three times more of a chance of being pregnant with a triphastic chart, than without.

The Bottom Line

Having a triphasic pattern on your BBT chart does not guarantee that you’re pregnant, but it does seem to be a good sign. However, it’s important to remember that some women show triphasic charts and are not pregnant. I have a friend whose BBT chart shows a triphasic pattern quite often, and she has not gotten pregnant.

It’s also important to remember that the greater majority of BBT charts do not show a triphasic pattern. So if you don’t see this third temperature shift on your BBT chart, you shouldn’t take that as a sign that you’re not pregnant.

More on how to get pregnant:

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Triphasic Pattern and Pregnancy: a Statistical Analysis. FertilityFriend.com. Accessed on January 1, 2009. http://www.fertilityfriend.com/Faqs/Triphasic-Pattern-and-Pregnancy.html

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