Temporal relation of ovulation to salivary and vaginal electrical resistance patterns: implications for natural family planning

An independent assessment of the CUE Monitor (Zetek, Aurora, Colorado) as an ovulation predictor was made with emphasis on its potential role in "natural family planning". The device provides a digital measurement of the electrical resistance of saliva and vaginal secretions. Twenty-nine menstrual cycles from 11 regularly cycling women were monitored with basal temperatures, urinary LH, pelvic ultrasound and the CUE monitor. Patterns of peak salivary electrical resistance were able to predict ovulation on average 5.3 (+/- 1.9 SD) days in advance. Despite variations in total length of the follicular phase from cycle to cycle, the within-subject variation of this predictive interval was quite small. Nadirs in the electrical resistance of vaginal secretions occurred within 2 days of ovulation in all but one patient. Variation in this interval from cycle-to-cycle was small as well. We propose an algorithm for the use of these intervals in "natural family planning" that could safely reduce the monthly abstinence period of present methods. The simplicity, objectivity and consistency of this device could result in their greater general acceptance.