Ovulation prediction by monitoring salivary and vaginal electrical resistance with the PEAK Ovulation Predictor.

We investigated the ability of the PEAK Ovulation Predictor to predict the expected date of ovulation in 21 infertile, spontaneously ovulating women. A nonsignificant correlation (R = 0.15; P = .51) existed between the predicted date of ovulation and the day of the serum LH peak. A moderately strong correlation (R = 0.61; P less than .01) was observed between the day of the salivary electrical resistance peak and that of the serum LH peak. However, the serum LH peak occurred between 4-9 days after an identified peak in salivary electrical resistance. Twice-daily urine LH testing correlated strongly with both the serum LH peak (R = 0.93; P = .0001) and the ultrasound-detected day of ovulation (R = 0.81; P = .0001). A statistically significant peak in the mean salivary or vaginal electrical resistance on a particular day relative to the day of the serum LH peak could not be demonstrated. When identified, the nadir in vaginal electrical resistance occurred no earlier than 2 days before the serum LH peak and thus may mark the endpoint of the fertile period for natural family planning methods. We conclude that, whereas the PEAK Ovulation Predictor is of little value in accurately predicting ovulation, measurements of salivary and vaginal electrical resistance may be helpful in timing inseminations. However, for detection of the serum LH surge, twice-daily urine LH testing demonstrated a stronger correlation and narrower frequency distribution than did those determinations based on electrical resistance.