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Taking temperature for BBT charting

You should take your temperature orally each morning before getting up, eating or drinking. Digital thermometers are used for their accuracy and ease of use. You can imagine the frustration involved in trying to see your temperature on a difficult-to-read basal thermometer in the morning. And, by the way, smoking is forbidden for women who are charting their basal body temperature (BBT) because of the inaccuracy it creates in measuring an oral temperature.

It is estimated that approximately 40 per cent of women suffering from infertility fall into the ovulatory dysfunction category. The basal body temperature chart certainly provides a significant amount of information with regard to a woman's ovulatory status.

BBT charting is a useful tool in the evaluation and treatment of infertile couples because of its ability to confirm ovulation. BBT charting also helps the couple understand more fully the physiological processes surrounding ovulation. Unfortunately, they cannot predict ovulation and can be affected by many factors resulting in inaccuracies. However, careful review of BBT charts with your GP will identify the most fertile times in your cycle.

The mechanism underlying the biphasic nature of an ovulatory BBT is the production of progesterone after ovulation. Progesterone is a thermogenic hormone which usually causes a rise in the basal temperature of 0.4 to 1.0 degrees Fahrenheit. Thus, after ovulation, and the production of progesterone by the corpus luteum, the basal temperature rises. When LH (the ovulatory trigger) measurements are correlated with BBT charts, it appears that the temperature rise usually occurs two days after the LH surge. The temperature elevation is associated with serum progesterone levels greater than 4 ng/ml. Ovulation usually occurs one day before the temperature rises. The temperature usually stays raised for 10 days. BBT evaluations only confirm, but do not predict, ovulation, and can be affected by many factors resulting in inaccuracies. Despite these limitations, it remains a useful tool in the evaluation and treatment of infertility and is often recommended.

New products are now being marketed that combine the useful information of the BBT with other hormonal measurements that fluctuate during the cycle. Combining these data may help to predict especially fertile times during the cycle with greater accuracy.

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