Body Temperature Charting

Congratulations! You've made the decision to start trying to conceive. If you're like me, the thought can be daunting. After all, most of us have spent months or years avoiding conception. When my husband and I started planning the beginning of our family, I wanted to make the process as quick and efficient as possible. I did some research and decided that I would begin to chart my basal body temperature (BBT) in order to maximize my chances of becoming pregnant. After 19 completed cycles I'm a firm believer in this technique.

I am not a medical professional, just someone who has accumulated some experience through trial and error. Before you begin, I would encourage you to read a book by a health educator in order to gain some in-depth knowledge about BBT charting. My personal favorite is Taking Charge of Your Fertility by Toni Weschler. I strongly recommend this book; it's a fascinating read that covers the how's and why's of charting in a fun, easy to read format. With that disclaimer, I'm going to attempt to cover the basics.

How Does Charting Work?

During your monthly menstrual cycle, two hormones share star billing. During the first half of your cycle (called the follicular phase) estrogen is the star. Estrogen helps your ovaries produce an egg that is released during ovulation. During the second half of your cycle (the luteal phase), progesterone takes over. The progesterone will dominate until it falls in anticipation of your menstrual period.

With that background, it's easy to explain the theory behind charting. Estrogen is a "cool" hormone. Progesterone is "warm". Prior to ovulation, when estrogen is dominant, your body temperature is marginally cooler than after ovulation, when progesterone is in charge. Given these facts, an increase in basal body temperature indicates that you have ovulated.

How do I get started?

One nice thing about BBT charting is that it requires little monetary investment. The only equipment you will absolutely need is a reliable thermometer. I prefer to use a digital basal thermometer, but any thermometer will do. Make sure that the thermometer you are using will measure to the .10 degree, as the temperature changes at issue in charting can be quite small. I bought a basal thermometer at WalMart for under $10.00. I prefer it because it beeps when it is ready to go, it lights up, and it stores temperatures so that they don't have to be recorded right away.

You will also need a graph that displays a range of temperatures along the days of your cycle. Most digital basal thermometers come with a sample graph that can be enlarged and duplicated on any copy machine. There is also a thorough sample chart in the back of Taking Charge of Your Fertility. The type of chart you use is a matter of personal preference. All that matters is that you have one place to record your daily temperature, so that you can spot the fluctuating temperature patters that occur during your cycle.

Some people prefer to do their charting on-line. There are two Web sites that provide this service. At http://www.fertilityfriend.com/you can download free software that allows you to post your daily temperatures. The software also gives hints about your cycle. Or, you can go to http://www.tcoyf.com/.

I have my thermometer, what do I do now?

Great, you're ready to get started! BBT charting measures basal temperature. Basal temperature is your temperature when you very first awaken in the morning. That means that you take your temperature before you stand up, go to the bathroom, take a sip of water, brush your teeth, talk on the phone, or kiss your spouse. In my routine, the alarm goes off and I stick the thermometer in my mouth. It's that simple.

To be accurate, the temperature must be taken at the same time every day. During the week, I get up at 5:30. I take my temperature at that time. That means that I must also take my temperature at 5:30 on the weekends. Fortunately, I don't have to fully awaken; I just let the thermometer do its thing and then I go back to sleep.

The easiest way to begin charting is to start at CD1, the first day of your cycle. Cycle Day One is the first day that you see true red menstrual flow. You simply take your temperature and record it on your chart. Typically, pre-ovulatory temperatures range from 97.0 to 97.6, although there is a wide range of "normal" temperatures. One day, you will notice that your temperature is higher than it has been on previous days. The general rule is that you have ovulated when your temperature rises .2 degrees higher than any temperature from the previous 6 days, and it stays elevated for at least 3 consecutive days. In general, post-ovulatory temperatures range from 97.7 upward.

So, will charting tell me when I'm going to ovulate?

Unfortunately, using a BBT chart will only tell you when you have ovulated. It doesn't predict ovulation. Occasionally, you may experience a temperature dip on the day of ovulation. This is caused by an estrogen surge right at ovulation. Unfortunately, this does not always occur. In order to predict ovulation, it is necessary to track your cervical mucous.

When your period is over, you may notice that your cervical mucous is sticky or chalky. As you get closer to ovulation the fluid will get thinner. Eventually, the mucous turns to the consistency of egg whites. This is egg white cervical mucous, and it is highly fertile. As a general rule, you and your partner should be intimate every day that you see egg white cervical fluid. Once your temperature increases after ovulation you will notice that your cervical fluid gets thicker or dries up all together.

Some women are able to check for cervical mucous externally. Some women don't have enough fluid to feel externally and need to do an internal check. This is most easily accomplished while sitting on the toilet. Just make sure you have clean hands, and use your index or middle finger to reach up towards your cervix. I realize that this seems odd, but it's the best way to gauge your fertility at any given time of the month. The analysis of cervical mucous, in combination with using a BBT chart, is a great way to pinpoint your fertile times. The rule to remember is this: You should have intercourse every day that you see fertile cervical mucous, and continue until you see a temperature rise. Following this rule will guarantee that you are intimate on the days that promise the best chance of conceiving.

What are other benefits of charting?

If you and your partner have normal fertility, you should achieve success within 4 to 6 cycles of charting your BBT. This occurs because charting and tracking your cervical mucous allow you to have sex during your fertile times. The egg only lives for approximately 24 hours, so timing is everything.

The chart also lets you pinpoint your normal cycle. It is a myth to assume that every woman ovulates on day 14 of her cycle. In fact, a woman's normal pattern can mean ovulation on day 10 or day 21. Using the chart makes it easy to find your normal ovulatory schedule.


In addition to rapid pregnancy achievement, charting can alert you to some potential problems or complications, including:

Anovulation. If your chart never shows a sustained bi-phasic pattern, characterized by the lack of a temperature rise, it is likely that you are not ovulating. Charting can alert you to this fact, allowing you to seek medical intervention.

A luteal phase defect. Ideally, the luteal phase is 14 days. A luteal phase shorter than 10 days can impair fertility, as it makes it difficult for the fertilized embryo to implant in the uterus. You can easily spot a short luteal phase on a BBT chart; it is seen by the absence of at least 10 high temperatures.

A thyroid condition. Both hyperthyroidism and hypothyroidism can impair fertility. An under-active thyroid can sometimes be seen in very low temperatures, while a hyper-active thyroid is manifested in unusually high temperatures.

Male factor infertility. If you are consistently having sex on your fertile days but fail to become pregnant, it may be due to a problem with your partner's sperm. Once again, charting can alert you to this fact and allow you to seek intervention.

This information is only the tip of the iceberg. I would encourage anyone considering charting to read Taking Charge of Your Fertility or a similar book. A wealth of information may also be found at The Waiting Game, StorkNet's Trying to Conceive message board forum where you can meet lots of other supportive women. Good luck! I hope all of you soon realize your dream of becoming mothers.