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.
PIP: This study assesses how closely basal body temperature (BBT) charts match detailed endocrine data in distinguishing ovulatory from anovulatory cycles, detecting short or inadequate luteal phase cycles, and determining the time of ovulation. 6 experienced physicians were asked to separately evaluate 104 BBT charts representing 98 women between 18-30 years of age. These physicians were to evaluate each chart for the presence of a biphasic pattern and to estimate the day of ovulation that they thought showed a biphasic BBT curve. Accuracy of estimation was judged by comparison with the day of the luteinizing hormone (LH) peak. Results indicate that: 1) the number of charts for which each physician correctly estimated the time of ovulation +or- 1 day of the LH peak ranged from 24-34, 2) although each physician correctly estimated the time of ovulation from an average of 38.1% of the charts, only 9 (22.1%) of the charts were correctly assessed by all 6 physicians, 3) an additional 22.1% of these cycles were thought to have monophasic patterns, 4) 37 (48%) of the charts drew a mixed response from the physicians, whose judgements differed regarding the presence of biphasic patterns or the correct day of ovulation, 5) in the 18 charts evaluating the short luteal phase cycles, the day of ovulation was assessed correctly in only one cycle by 2 of the 6 physicians, and 6) the anovoluntary cycles were uniformly found to have monophasic patterns by all evaluators. Extreme caution in interpretation is urged when BBT is used for clinical or research evaluations of ovualtion or menstrual cycle dynamics.