Abstract: A menstrual cycle meter which comprises a casing microprocessor-based electronic circuitry including calendar keeping means and calculating means, a plurality of buttons provided on the casing to enable the microprocessor to receive user-input commands and/or data including the first day of at least the last two menstrual cycles of a user, and a display (12) provided on the casing and under the control of the microprocessor to display indication relating to the calculated fertile and infertile periods of the current menstrual cycle according to the stored input data. The display includes visual indicating means (58 & 59) for indicating the expected sex of a baby that is likely to be conceived in a particular day during the fertile period.