Vaginal discharge is not necessarily a precise sign of ovulation. A more precise indicator of ovulation is a slight increase in body temperature that is noticeable only if you’ve measured the body temperature every day during the whole menstrual cycle. Another way to predict ovulation is using an ovulation predictor kit (OPK). OPKs detect a peak in luteinisating hormone (LH) in the urine that happens just before ovulation. If you measure, body temperature you can observe ovulation only after it has happened. If you use an ovulation predictor kit you may predict ovulation several hours before it really happens.