Optimal features of basal body temperature recordings associated with conceptional cycles.

Oral basal body temperature (BBT) recordings of 46 women that conceived by donor insemination and who had midcycle monitoring of luteinising hormone (LH) were analysed to establish features associated with an optimal cycle. All cycles exhibited a biphasic temperature shift associated with the follicular (mean + SD, 36.5 degrees C +/- 0.22) and luteal phases (36.8 degrees C +/- 0.19). Whilst a mean body temperature rise occurred on Day +1 when all cycles were analysed, individual patterns were seen at ovulation including no change or a decrease in BBT between Day 0 and Day +1. The BBT of the postovulatory phase was stable and only 4.5% of the 644 observations made showed a change of more than 0.2 degrees C from day to day. It was concluded that the BBT charting has limitations when used to recognize the day of ovulation, and that some variable patterns of the early luteal phase are consistent with conception. Finally, optimal luteal phases demonstrated remarkable stability.