An electronic
system for determining a time of the temperature
nadir of a female human during the
menstrual cycle comprises a wearable device (1) that includes a first
sensor system (104), configured to determine a temperature of the female human, and a second
sensor system (101, 102, 103), configured to determine one or more further physiological parameters of the female human. The electronic
system further comprises a processor (13, 30, 40), configured to determine a detected starting point of the
fertility phase of the female human, using the one or more further physiological parameters of the female human. The processor (13, 30, 40) is further configured to detect the temperature
nadir as a temporary decrease in the temperature, using the detected starting point of the
fertility phase of the female human. The time of the temperature
nadir is used as an indicator of the time of
ovulation and peak oestrogen level.