Basal Body Temperature
courtesy: www.ivillage.com

What is basal body temperature? Basal body temperature (BBT) is the temperature of your body at rest.

Why would you measure your BBT? BBT charting is a useful tool for couples trying to conceive because of its ability to confirm ovulation. BBT charting also helps the couple understand more fully the physiological processes surrounding ovulation. Not all women ovulate 14 days before their next period. In fact, for many women, the time between ovulation and their period (called the luteal phase) is shorter. A woman needs to have at least 10 days in this phase in order to allow enough time for the fertilized egg to reach the uterus and implant. If it is less, she will need to resolve the short luteal phase if she desires to maintain a pregnancy.

Is BBT charting enough? No. Charting temperatures will only tell you when ovulation has already occurred. Since an egg can only live about 12 to 24 hours, by the time your temperatures rise a day or two after ovulation, the egg will already be gone. So when charting your fertility signs in order to time intercourse, it is most useful to chart your cervical fluid to determine when you are in your most fertile phase.

How do you take your BBT? Your BBT is taken orally with a special BBT thermometer. This type of thermometer is graduated in easy-to-read one-tenth degree increments. Your temperature must be taken before any activity, first thing in the morning, after at least three hours of consecutive sleep. The thermometer must be shaken down the night before, because even this activity can raise your temperature -- and you are looking for as little as two-tenths of a degree of difference. Be sure to read the instructions that come with the thermometer. They are usually very complete.

What BBT changes can you expect during your cycle? Your BBT is lower during the first two weeks of the menstrual cycle, prior to ovulation. The presence of the hormone estrogen keeps the BBT low. Typically it will range from 97.0 to 97.5 degrees Fahrenheit. Immediately following ovulation, progesterone "turns up the heat" a bit, and there is typically a rise of at least 0.4 to 0.6 degrees until the time of your next menstrual period. This temperature rise will let you know that ovulation has occurred.

How can you chart your BBT? Using either a notebook or graph paper, start recording on day one of your menstrual cycle -- the first day of your period. For each day, record your temperature, any reason for a variation in temperature (if applicable), if you made love that day, and if you were menstruating. This charting will not only be invaluable to you but will provide your health care provider with important information in helping you achieve your fertility goals -- of achieving or avoiding pregnancy.

What factors can affect your BBT? Your temperature can be affected if you didn't get a good night's sleep, if you didn't have at least three hours of consecutive sleep after making love, if you have a fever or if you had an alcholic drink the night before.

Can you detect pregnancy by BBT changes? Yes. If your BBT remains elevated even past the time that your menstrual period is due, it could be a very early indicator of pregnancy. When you conceive, the egg is fertilized in the fallopian tube, after which it takes about a week to travel to the uterus, where it will implant. It is at this time that your body is finally able to detect that you are pregnant. When hCG is released, women often experience a third temperature rise, not as dramatic as the first, but can usually be seen anywhere from about a week to 12 days after the first temperature rise.