Basal body temperature chart pregnant vs not pregnant

Triphasic charts are basal body temperature (BBT) charts containing three different temperature rises. These patterns are generally thought to be possible signs of pregnancy, and due to this, the charts are coveted throughout the fertility charting community in Australia.

When you get this pattern on your BBT chart, you will have hopes of getting a positive result after doing a pregnancy test. You may even start to have a sudden awareness of some early signs of pregnancy.

Some questions most women in Australia have concerning triphasic BBT charts include:

• How do I spot a triphasic chart? What are the causes of the pattern?
• Is this a reliable sign of pregnancy?
• Is the excitement of getting this justified?

Overview of triphasic charts

Before we cover more on the triphasic chart, let’s first define biphasic. Each BBT chart that shows ovulation is biphasic, and bi stands for two, while phasic means linked to a phase. There will be two distinct temperature phases on a basal body temperature chart with ovulation – one before you ovulate and the other after ovulation.

Ovulation is indicated on the basal body temperature chart by the distinct and sustained increase in body temperature. If you check the sample chart, you will notice the temperatures before the 15th day of the cycle are generally lower than those after the 15th day if you have a regular menstrual cycle. This is how you will know that the ovaries have released an egg on day 15, as shown in the chart above.

With a triphasic chart, you will see three temperature shifts. Tri stands for three, which you likely already know. The temperature shift should occur about seven days after you ovulate for the chart to be triphasic. When you look at this chart above, do you see a temperature shift beginning on the 24th day?  The change occurred on day 11th after ovulation, but even if it had started earlier, maybe like seven days after the egg is released, it still indicates that the chart has a triphasic pattern.

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Reliability of triphasic charts

One fertility charting online software company conducted an informal analysis to evaluate their website’s basal body temperature charts and see if the triphasic patterns may indicate pregnancy. This was not peer-reviewed scientific research, but the results were interesting.

During their informal analysis, they did consider the triphasic pattern to be the second significant upward temperature shift of about 0.17℃, occurring about seven days after ovulation. (Generally, there isn’t an actual definitive definition of a triphasic chart. The people who compare and share BBT charts may disagree on whether the patents could be considered triphasic or not. Our definition here is for the analysis.)

When they analysed more than 149,000 BBT charts, the researchers realised that 12% of the pregnancy charts revealed a triphasic pattern. After taking a look at the non-pregnancy chart, they found out that 4.5% of them showed a triphasic pattern. Triphasic shifts were detected on average on the 9DPO. 

Basal body temperature chart

Therefore based on these statistics, a basal body temperature chart that indicates a triphasic chart is three times more likely to belong to a pregnant woman than a non-pregnant one.

Another essential fact we shouldn’t forget to point out is that while 12% of the pregnant women charts had a triphasic pattern, 88% of them did not. When you compare BBT charts for 100 pregnant women, only one or two of the charts will show a triphasic pattern. However, if you do not see the pattern, it does not mean that you are not pregnant.

It’s also important to note that having a triphasic chart does not necessarily mean you conceived. As the data has shown above, about 5 out of 100 charts of women who have not conceived still showed a triphasic pattern. This means that some women can regularly get a triphasic pattern on their BBT charts, but they are not pregnant.

What causes triphasic temperature shifts

What is the likely cause of the third temperature shift on a basal body temperature chart?

For a non-pregnant woman’s chart, the triphasic chart may occur due to the varying bedroom temperatures, hormones getting excited, or a slight illness that does not cause a fever but a slight temperature rise.

For a pregnant woman, the triphasic chart may be caused by an increase in the progesterone hormone in the body. Hormone progesterone causes the normal temperature to increase during the ovulation period. Progesterone will trigger your uterine lining to prepare for embryo implantation after fertilisation. It also suppresses ovulation, the reason why you cannot get pregnant when you have already conceived. It also ensures that the endometrium does not shed when you already have an embryo or baby in the uterus.

The assumption is that implantation of the embryo will trigger and increase the production of progesterone hormone, and the suddenly increased levels of the hormone will cause another temperature shift.

When is the best time to take a pregnancy test?

Most women who think that they are pregnant will be eager to take a pregnancy test during the early days to confirm if they did conceive. This is especially true for women who have been trying to conceive for some time and cannot wait to get the big fat positive or maybe not.

There are plenty of good reasons to wait until the two-week wait period before taking a pregnancy test. You may assume that a triphasic pattern is an excellent reason to go ahead and take a pregnancy test before you miss your periods, but this is not the case. 

Keep in mind that pregnancy tests look for the hCG hormone or pregnancy hormone and not progesterone. Therefore if your progesterone levels are high, that does not necessarily mean that your hCG hormones are also high.

There is a chance that you will get a big fat negative, also known as a false negative, even if you did conceive, and this is not ideal. You may be tempted to engage in careless habits when you are already pregnant, affecting your pregnancy’s health. The best thing to do is to hold off on the testing until you miss your periods or day your chart shows 16 days of high temperatures. Sixteen days of high temperatures are one of the best pregnancy signs you will find on your basal body temperature chart.

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Conclusion

A basal body temperature chart is an ideal way to understand your menstrual cycle better, identify the ovulation days, and know the most fertile days of your menstrual cycle. Regardless, you may be tempted to check pregnancy signs on your chart like a triphasic pattern, but the ideal sign of pregnancy on a basal body temperature chart is that the luteal phase has passed 16 days. In simple terms, you will have missed your periods, or it will be a few days late. Although you may indeed see a triphasic pattern on your chart when you are pregnant, the pattern does not necessarily confirm pregnancy. Besides, not seeing the triphasic pattern does not mean you are not pregnant.

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