Basal Body Temperature Charting
BBT charting is one of the most time-tested ways to track your fertility status. In the “old days”, basal body temperature charting involved a pencil and piece of graph paper by your bedside. Functional? Certainly. Pleasant? Not so much...
Charting your basal body temperature at OvaGraph, on the other hand, is quick and easy. And we promise that the graph you create will be much more informative (not to mention prettier) than the paper graph of yesteryear! (Visit Fairhaven Health online to purchase a basal thermometer.)
In simple terms, your basal body temperature is the temperature at which your body rests, which tends to be a bit lower than your “normal” temperature, usually 97 point something degrees F versus 98.6 degrees F. By taking your BBT each morning throughout your cycle you will be able to detect the natural rise in your basal body temperature that occurs just after ovulation. This post-ovulatory shift in BBT is due to the hormone progesterone, sometimes referred to as the “warming hormone”. After ovulation, the corpus luteum (a fancy Latin word for the structure that remains after the ovarian follicle releases the egg) produces progesterone, which helps a fertilized egg implant into the wall of the uterus. This increasing amount of progesterone causes the body to warm up, which is reflected in an increase in your BBT.
If you are trying-to-conceive, BBT charting can provide valuable information about your menstrual cycle and your fertility status. First and foremost, BBT charting will allow you to pinpoint the exact day (or pretty close to the exact day) that you ovulated. The BBT shift occurs just about a full day after you ovulate. As you chart your BBT daily, you will notice your chart will become “biphasic”, meaning that it will show relatively low temperatures before ovulation and slightly higher temperatures after ovulation. It is important to note that this BBT shift is actually quite subtle, with temperatures typically rising by only .4 degrees F (.2 degrees C) after ovulation, and sometimes even less. It is important to note that you might see rapid rise in your BBT, or you might see an incremental rise, or it may even rise and fall slightly over several days. Due to this variability, it is important to chart for several cycles to understand the specific way in which you experience this BBT shift. Once you know the cycle date upon which you usually ovulate, you can then predict your fertile window for the next cycle and, therefore, plan your “baby dancing” appropriately.
To be able to detect this very subtle rise in temperatures requires that you are consistent about how and when you take your daily temperature (see below) and that you are diligent and accurate in your record keeping (made simple with OvaGraph.com!). In addition, you will need a special basal body thermometer, like the digital basal and glass basal thermometers sold at Fairhaven Health.
Along with helping you to pinpoint the date of ovulation, BBT charting can also help you identify potential fertility issues. Charting your temperatures will reveal the length of both the follicular phase (the days between the start of your menstrual period until ovulation) and the luteal phase (the days between ovulation and the start of your next period) of your menstrual cycle. While there is a wide variation among women of follicular phase lengths, it is generally accepted that a “normal” luteal phase is approximately 14 days. A luteal phase of at least 14 days will allow sufficient time for implantation of a fertilized egg. If, however, the luteal phase lasts only 10 days (or less), you might have what is known as a luteal phase defect. While a shortened luteal phase can result in early miscarriage, fortunately it is most often easily treatable with the help of a medical provider. BBT charting can help you determine the length of your luteal phase, giving you information to share with your doctor if you think it might be too short.
One last benefit of BBT charting: it can give you an early clue that you might be pregnant! A typical BBT pattern will often show a dip in temperatures just before you are ready to start your menstrual period. If your temperatures remain elevated in the last few days of your menstrual cycle, it might be worthwhile to take a pregnancy test!
BBT charting is really quite simple, although it does require a commitment to carefully taking your temperature each day. Here’s how to go about it:
- Using your digital basal thermometer, take your temperature (typically done orally, although some women prefer to take vaginal or rectal temps) first thing in the morning after sleeping for at least 3 hours, and before you get out of bed. It is important that you move as little as possible before taking your temperature, as even slight movement can cause your BBT to rise. For convenience, it is usually best to store your thermometer near your bedside so that you don’t have to move much to reach it. If you use a glass thermometer, make sure you shake it down before going to bed.
- Take the temperature at as close to the same time each day as possible, trying to stay within a half-hour window. Some women find it helpful to set an alarm so they don’t oversleep and miss their BBT window.
- Enter your temperatures at Ovagraph.com each day, so that you can easily observe changes in your temperatures on the graph. After ovulation has likely taken place, many women see a thermal shift of approximately .4 degrees F.
- If you happen to oversleep, or miss a day, don’t worry! You should still be able to recognize the shift. Just be sure to continue with your charting through the rest of your cycle, and be sure to make careful notes on days where changes in the routine may have impacted the temperature reading.
- If you are not able to detect a shift in BBT in the course of a cycle, it is mostly likely due to inconsistencies in the timing and method of taking your temperature, or perhaps due to an error in charting. In the next cycle, try to be even more diligent about how you go about these things. If, however, you move through several cycles without seeing a BBT shift, it is possible that you are not ovulating, and you should consult your physician.