Basal body temperature: unreliable method of ovulation detection.

Basal body temperature (BBT) charts for menstrual cycles of 98 women were evaluated by six experienced physicians. The time of ovulation as estimated from the charts by a consensus of at least five of the evaluators coincided with the luteinizing hormone (LH) peak +/- 1 day in only 17 (22.1%) of the 77 cycles that were determined by endocrine profiles to be ovulatory and to have adequate luteal phases. An additional 22.1% of these cycles were thought to have monophasic patterns by a consensus of the physicians. Extreme caution in interpretation is urged when BBT is used for clinical or research evaluations of ovulation or menstrual cycle dynamics.