Basal Body Temperature: What Does it Say About Fertility and Does BBT Tracking Actually Work?

What does temperature, ovulation, and getting pregnant have in common? Turns out – quite a lot! 

Intrigued?

Read on to learn exactly what your basal body temperature (BBT) is, what it says about your fertility, and how you can benefit from tracking it based on your fertility goals. We’ll also introduce you to the newest member of the Mira family – our Basal Body Thermometer! 

What is BBT?

Basal Body Temperature or “BBT” for short is a measurement of the body’s temperature when it is completely at rest. BBT thermometers are designed to measure BBT down to a tenth of a degree – which is why they can be used to track very slight changes in body temperature over time. 

It’s important to note that BBT is not the same as regular body temperature. BBT can only be measured when the body is at rest. This is why BBT measurements must be taken first thing in the morning after the body has been asleep. 

What Does BBT Have to Do With Fertility?

A rise in BBT is a sign that ovulation has occurred – here’s why. 

At the start of the follicular phase (i.e. day one of your period), estrogen, progesterone, and luteinizing hormone (LH) levels are low. 

Within just a few days (depending on the length of your cycle), estrogen begins to rise gradually. Then, approximately midway through the cycle, LH rapidly increases to trigger ovulation. After ovulation (during the luteal phase), LH returns back to its baseline and estrogen gradually decreases. 

Progesterone, on the other hand, rises throughout the first half of the luteal phase before falling again in the week or so before your period begins. This rise in progesterone after ovulation is linked to a noticeable rise in BBT, which lasts for the remainder of the menstrual cycle. This increase is typically around 0.5 degrees Fahrenheit (or up to 0.3 degrees Celsius).

So to put it simply: BBT has a lot to do with fertility! This is because it is one of the many natural symptoms of ovulation. 

 

5 Things BBT Can Tell You About Your Fertility

When measured and tracked daily, BBT can tell us a lot about our fertility status – here are five key examples. 

Ovulation

A slight rise in BBT is a good indicator that ovulation has occurred. This is particularly helpful for individuals looking to better understand their cycles and ability to conceive. 

Cycle characteristics

BBT tracking can provide you with a full picture of what your “typical” cycle looks like. For example, you can learn how long your cycle typically lasts, at what point within your cycle ovulation usually occurs, and whether or not you experience irregular ovulation. 

When to have sex to plan a pregnancy

Over time, BBT tracking enables you to see when you are most likely to ovulate. And by estimating your day of ovulation, you can also estimate your fertile window. You can then plan to have sex with your partner during this time in order to maximize your chances of conception. 

When not to have sex to avoid pregnancy

On the flip side, BBT tracking can also be used as a way to prevent pregnancy. By estimating ovulation and your fertile window, you can proactively avoid having sex during this period of time when the chances of conception are at their highest. 

If you are pregnant

Elevated BBT levels are also an early symptom of pregnancy. So if your BBT does not go back down around the time of your period, this could be a very early sign that you are pregnant. 

Does BBT Tracking Actually Work? Let’s Look at the Stats 

In a research study of 30 menstruating women, BBT tracking was 80% effective at estimating ovulation. In another study involving a mobile app, BBT tracking alongside the documentation of cycle dates was found to be over 91% effective at preventing pregnancy. 

However, it’s important to note that the effectiveness of BBT tracking depends greatly on the accuracy and consistency of the user. For example, if you miss a date or if you record an incorrect temperature, this can throw off your tracking and reduce effectiveness. 

At Mira, we see the process of measuring and tracking BBT as an excellent way to get to know your body better. By familiarizing yourself with the biological markers of fertility (such as BBT), you can make more informed decisions – no matter what your reproductive objectives are. 

Introducing Our New Product: Basal Body Thermometer

We want you to learn everything you can about your fertility, and that’s why we are SO excited to introduce you to Mira’s own basal body thermometer! 

This thermometer is designed to help you measure and track your BBT, so that you can effectively plan (or avoid) pregnancy. 

It’s the perfect tool for individuals and couples who are:

• Wanting to learn more about their unique menstrual cycle patterns and milestones
• Thinking about planning a pregnancy now or in the near future
• Looking for a natural family planning (NFP) method

When used together with the calendar function in the Mira app, this basal body thermometer is the perfect sidekick to help you achieve your fertility goals! 

Step-By-Step Guide to BBT Monitoring With Mira

Measuring 

Take your thermometer out of the box and find a home for it near your bed – for example, in the drawer of a bedside table. 

Each morning right after you wake up, take your thermometer, turn it on, and place it under your tongue for 60 seconds. Your results will then be displayed digitally on the thermometer. For the most accurate results, try to take your BBT at the same time each morning. 

Once measurement is complete, rinse off your thermometer, turn it off, and return it back to its place.  

Tracking

Once your results are displayed, there’s no need to worry about charting them out on a piece of paper. Instead, the Mira BBT thermometer syncs automatically with the Mira app; storing and charting your data for you. 

Interpreting the charts

It will take several cycles (at least three) before you will start to notice any patterns with your BBT charts. 

Once you have at least three cycles’ worth of data, you may start to notice some trends. Here are a few scenarios that may occur:

• Your BBT line is consistently low (in the first half of each cycle) and then consistently higher (in the second half of the cycle): This is considered a “normal” BBT chart reading, as it shows that your temperature is elevated after ovulation before returning back to baseline levels at the start of your period. 
• Your BBT line is consistently flat: If your BBT measurements create a flat line with no clear patterns or any highs or lows, this could indicate that your body is not ovulating. 
• Your BBT line displays a zigzag shape: If your BBT measurements appear to be all over the place, this could indicate a hormonal imbalance. It could also be a reflection of illness, fatigue, stress, lack of sleep, or inconsistent measuring.

 

Accurate and consistent BBT measuring can take some time to get used to. If you’re still not getting the hang of it after at least six months, it may be worth exploring other fertility awareness methods. If you are concerned about your results, make an appointment with your doctor and they can provide the best advice for your individual situation. 

I’m Pregnant! Do I Still Need to Track BBT? 

Once you have confirmed a pregnancy with a pregnancy test, there is no medical need to continue tracking BBT daily. Instead, focus your energy on setting your pregnancy up for success by:

• Making sure you’re taking a daily prenatal vitamin with folic acid
• Stopping the consumption of alcohol, tobacco, and potentially harmful foods
• Arranging to see your doctor for a health check 

You should also be proactive about reducing stress by setting aside plenty of time to relax, rest, and spend time doing activities you enjoy. 

Deciding if the BBT Method is Right for You

BBT tracking isn’t always a good fit for everyone. For example, the following scenarios can interfere with your body temperature, making it difficult to obtain accurate measurements: 

• Being emotionally or physically stressed on a regular basis
• Regularly consuming alcohol, drugs, and certain prescription medication
• Insomnia, sleeping difficulties, or jet lag
• Having a fever

Additionally, because BBT tracking must be done at the same time each morning, it may not be a good fit for those who struggle with routine or those who work inconsistent schedules (particularly night shifts). 

In unique cases, it’s also possible for ovulation to occur without any noticeable increases or decreases in BBT, which can make the tracking process difficult.  

Improving Accuracy: Are There Other Fertility Tracking Options Available? 

Yes! BBT monitoring is just one of many tools that you can use to track your fertility. 

For example, with Mira’s palm-sized hormone lab, you can measure up to four key fertility hormones from the comfort of your own home with 99% lab-grade accuracy. 

From predicting and confirming ovulation to getting a better understanding of how far away you are from menopause, the Mira analyzer empowers you to better understand your body so that you can make confident decisions about your reproductive health.