Descriptive analysis of the relationship between progesterone and basal body temperature across the menstrual cycle

Abstract

ObjectiveDescribe the relationship between basal body temperature (BBT) and pregnanediol-3 alpha-glucuronide (PDG, the urine metabolite of progesterone) across the menstrual cycle.Design: Observational study.Setting: Study carried out from 1996 to 1997 in eight European family planning clinics.Participant(s): One hundred and seven normally fertile and cycling women.Main outcome measure(s): BBT and PDG level on each day of 283 cycles and ultrasound determination of the day of ovulation. Result(s): In comparison with previous end-of-cycle levels, decreases in PDG and BBT on the first day of menses were seen in nearly 90% and 80% of cycles, respectively. In a non-negligible percentage of cycles, luteolysis would continue during menses: between the second and the third day after menses, small but significant decreases in PDG and BBT were seen in 76% and 48% of cycles, respectively. During the peri-ovulatory phase, between the third and the second day before ovulation, PDG and BBT began to rise in 56% and 41% of cycles, respectively. There was a medium degree of correlation between PDG levels and BBT (r = 0.53; 7,279 days with available measurements). The relationship between PDG levels and BBT was linear at low PDG levels but BBT increased no longer when PDG levels continued to rise above a threshold of nearly 10 mcg/mg Cr. Conclusion(s): PDG and BBT had parallel increases at low PDG rates but diverged at higher rates.