Are you trying to conceive or wondering if you might be pregnant? Your BBT chart can tell you a lot about your fertility, especially whether you are pregnant or not. From understanding the basics of when BBT drops or rises and how to interpret your chart, we can uncover everything you need to know to use this powerful tool on your fertility journey.
What is basal body temperature?
Basal Body Temperature (BBT) is the lowest temperature of your body at complete rest. BBT changes throughout the menstrual cycle, reflecting fluctuations in hormone levels. During the first half of the cycle, estrogen dominates and causes the body to produce more cervical mucus, which creates a lower, more stable BBT.
After ovulation, progesterone takes over and causes a slight increase in temperature. Resting temperature is best measured first thing when you wake up in the morning, before you get out of bed, eat, drink, walk, or talk.
How to use BBT to know if you have ovulated
Throughout a woman’s cycle, BBT typically follows a pattern—lower temperatures before ovulation, followed by a rise afterward due to hormonal changes. Specifically, as progesterone increases after ovulation, BBT rises by about 0.5 – 1ºF (0.3 – 0.6ºC). To track this, you’ll need a basal thermometer and should take your temperature each morning right when you wake up.
Tracking manually can be tricky, but using an app like Premom makes it much easier by recording and charting your temperatures. With consistent tracking, you may notice a temperature shift that tends to occur 1-3 days after ovulation. This shift, known as the BBT Spike, can help you feel more confident that ovulation has likely occurred for that cycle.
If you’re using a regular digital basal thermometer, Premom’s unique Auto-Scan feature lets you log your temperature in seconds—just scan your thermometer with your phone’s camera and you’re done. It’s one of the fastest and simplest ways to record and track your basal temperature.
Pregnant BBT chart vs not pregnant
Progesterone naturally decreases right before your period starts if you’re not pregnant. However, it stays elevated if you are pregnant, making BBT a potential early clue to pregnancy!
So, what does a BBT pattern normally look like when not pregnant versus when you are pregnant? Let’s take a look at some Premom Pregnant BBT Charts and Not!
BBT chart not pregnant
Here is what a BBT chart looks like if you are not pregnant…
If pregnancy does not take place, your BBT chart will typically show a drop in temperature a day or two before your next menstrual period begins. This BBT drop is due to the decrease in progesterone levels in your body. Progesterone naturally decreases when you do not conceive during that menstrual cycle. If you are tracking your BBT consistently throughout your luteal phase (second half of the menstrual cycle), you may notice a dip in BBT right before the start of your next period or even the days before your period begins.
Pregnant BBT chart
Here is what a BBT chart when pregnant would look like…
A pregnant BBT chart will typically show a sustained rise in temperature due to the increased production of progesterone in your body, which helps support the pregnancy. Typically in early pregnancy, progesterone should not be dropping; therefore, your temperatures typically do not drop either. This sustained increase in temperature on the BBT chart can be a strong indicator of pregnancy, particularly if it persists for at least 15 days after ovulation. However, it’s important to note that not all women will experience a sustained temperature rise, and some may have other symptoms or signs of pregnancy.
BBT charts can vary from person to person. There is no single basal temperature chart if pregnant or not pregnant that applies to everyone. However, these are some general trends that can be observed in BBT charts for pregnancy and non-pregnancy. A sustained increase in temperature for more than two weeks after ovulation is a common indication of a pregnancy in a BBT chart.
How long does BBT stay elevated if pregnant?
During pregnancy, you won’t see a drop in BBT like you typically would right before the start of your period. Progesterone remains high throughout the pregnancy, meaning your temperature will typically stay high throughout the entire pregnancy as well. An elevated BBT result is not a definitive sign of pregnancy. If you suspect you might be pregnant, it’s best to take a pregnancy test or call your healthcare provider.
Does BBT drop after implantation?
BBT does not drop after implantation; however, some women might see a slight dip in BBT during the luteal phase, usually just about 24 hours. This is due to a second surge of estrogen that happens in the luteal phase, and when estrogen rises, that causes BBT to drop slightly. Your temperature should rise again the next day, and this quick dip is nothing to worry about.
Illness, stress, alcohol, travel, and sleep changes can affect your BBT. Instead of focusing on one reading, look at the overall trend throughout your cycle. Daily fluctuations are normal.
You can easily keep track of your BBT readings in the free Premom app. You’ll be able to see your BBT readings in correlation with your LH surge to see if and when you ovulated. This also allows you to easily see what happens to your BBT right before the predicted start of a new cycle, which could be an early indicator of pregnancy.
References
- Physiology, Ovulation and Basal Body Temperature- NCBI bookshelf. (2022). Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK556096/
- Grant, A., & Smarr, B. (n.d.). Feasibility of continuous distal body temperature for passive, early pregnancy detection. PLOS Digital Health. Retrieved from https://journals.plos.org/digitalhealth/article?id=10.1371%2Fjournal.pdig.0000034
- Basal body temperature: Family planning method. Cleveland Clinic. (n.d.). Retrieved from https://my.clevelandclinic.org/health/treatments/21065-basal-body-temperature
