Temporal relationships between indices of the fertile period.

The intra- and interwoman variation in nine physiologic or biochemical indices of the fertile period has been studied over 58 menstrual cycles from 13 experienced users of the symptothermal method of family planning by periodic abstinence. The time and duration of a possible fertile period have been determined by five methods (symptothermal, cervical mucus, basal body temperature plus calendar calculation, defined changes in the concentration of estrone-3-glucuronide and the ratio of estrone-3-glucuronide to pregnanediol-3 alpha-glucuronide as determined by immunochemical tests on daily samples of early morning urine). The values were compared with a period of probable fertility (day of urinary luteotropin [LH] peak -3 to day of LH peak +2). The duration of the possible fertile period by each method (mean +/- standard deviation) was 13.4 (2.9), 11.9 (2.9), 11.8 (3.3), 9.3 (2.2), and 10.9 (2.3) days, respectively, while the percentage of the probable fertile periods covered entirely by each approach was 98%, 91%, 90%, 83%, and 84%, respectively. The results warrant the initiation of clinical trials to ascertain the practical value of the individual or combined tests for family planning and the management of infertility.