Problems in using basal body temperature recordings in an infertility clinic.

Basal body temperature recordings are extensively used to diagnose and treat infertility, but too great an emphasis on the interpretation of these charts might be counter-productive in managing these patients. Several gynaecologists who use temperature charts clinically were asked to score 60 charts taken from a selection of normal and infertile women, and their results were compared with those obtained by a group of non-experts. Since the full hormonal profiles had been obtained for each of the 60 charts the accuracy of the predictions could be assessed. About 80% of the temperature charts were correctly interpreted by both groups as being either ovulatory or anovulatory but the day of ovulation was predicted correctly for only about 34% of the charts. When the charts were examined retrospectively the thermal nadir was found to coincide with the luteinising hormone surge in 43% of the charts from normal subjects but in only 25% of those from the infertile patients. Predicting the day of ovulation from the temperature recording, particularly in infertile women, is clearly unjustified.