[A simple method for estimating the day of ovulation by basal body temperature chart (author's transl)].

A new method for estimating the day of ovulation was assessed. The method is as follows; The range of hypothermic phase presumed 0.1 degrees C around mean basal body temperature of early 10 menstrual days. The day of ovulation was estimated by searching for the day which is followed by at least 4 consecutive days of rising temperature within the range of hypothermic phase. The accuracy of this method was assessed by comparing the basal body temperature and urinary luteinizing hormone (LH) peak day. The estimated day fell within 2 days during which the ovulation will occur most probably in 36 cycles (69%) and fell within 4 days around most expectable ovulation time in 46 cycles (88%). This result provide some insight into the limitation of the basal body temperature which is influenced by factors other than progesterone in determining the time of ovulation. But our simple objective method is useful in some cases than any other method determined by vague criteria.