according to the present invention means are provided for an accurate prediction of approaching ovulation by monitoring changes in cervical mucus secretion by the use of a vaginal probe with two electrodes only located close to the tip of the probe and thus near the entrance of the cervix . the two electrodes ar covered during the measurement by the mucus secreted by the cervical glands which descends into the vagina . a high frequency current of i is sent through the two electrodes into the vagina . this current is carried by electrons via the metal conductors and via ions in the mucus , resulting in an interface impedance z . the voltage drop v across z is i × z . v is measured by a simple amplifier connected with the two electrodes and from v it is possible to calculate z as v / i . with approaching ovulation , secretion of cervical mucus increases and the interface polarization impedance z decreases and measurements carried out on a daily basis result in a graph , such as shown in fig3 . for simplicity the variable measured named &# 34 ; vaginal impedance &# 34 ; is used , even as in reality the variable measured is the polarization impedance of the metal electrode / cervical mucus interface . a device of the invention is illustrated schematically in fig5 where 21 is the body of the probe , 25 are the two electrodes and 24 and 26 are the leads leading from the two electrodes , respectively . the probe with the two electrodes enables a much higher dynamic range of the measurements and the results which are achieved using this probe are more accurate than those which were achieved with the four - electrode probe . it is also simpler , cheaper for manufacture and also the electronics needed is simpler and considerably less expensive . it is advantageous to combine the measurement of the impedance with a measurement of the basal body temperature ( bbt ) of the woman examined . it has been known that there exists also a correlation of this parameter with the process of ovulation and the combined evaluation of both parameters provides increased accuracy and re liability in the determination of the fertile and infertile phases of the menstrual cycle as they were monitored during the field tests . in order to make it even more powerful , the rhythm method formula is also integrated into the software of the device as support for unpredicted changes which might occur due to irregularity of the menstrual cycle . a device according to the invention for measuring both electrode polarization impedance as well as temperature is illustrated with reference to fig2 in which 11 is a probe adapted to be inserted into the vagina ; which probe contains electrodes 12 and 13 , at a certain distance from each other , one of which , 12 and 13 is connected to a 500 hz to 100 khz current source 14 , and to amplifier 15 , the second being connected to the amplifier 15 via wire 17 . this amplifier 15 , is connected to rectifier 18 which is connected to dual - input a / d converter or v / f converter 19 , which is also connected with the temperature sensor 20 in probe 11 via signal conditioner 21 . the a / d or v / f converter 19 is connected with digital processor 22 and to display 23 . the digital processor 22 computes the relevant data based of an algorithm relating to the impedance measurement by the probe 11 when mucus 24 is between the two electrodes 12 and 13 , and on the temperature measurements by sensor 20 . the input is passed via two distinct channels and computed separately , the results being used to provide the desired information , which is used to actuate the display which can be by way of lcd color - led or by an audio signal or both . according to a preferred embodiment of the invention the probe carries also accurate temperature measuring means , and the results of the two measured parameters ar integrated to provide a reliable and accurate prediction of the fertile and infertile phases of the menstrual cycle . fig3 illustrates the results of cervical mucus polarization impedance measurements over an entire menstrual cycle , where a clear minimum is observable which is obtained when the electrode polarization impedance is at its lowest level , and the amount of cervical mucus is at a maximum . a typical graph of such measurements is given in fig8 showing both parameters . fig4 demonstrates that the variable monitored by the two - electrode probe is indeed the &# 34 ; electrode polarization impedance &# 34 ;. in order to prove this in some subjects daily vaginal measurements with the two - electrode probe were performed at a number of frequencies between 2 khz and 200 khz . it is known from the electrochemical theory of electrode polarization that on a log / log graph the relationship between electrode polarization impedance z and the frequency of the measuring current will be a straight line with a slope alpha smaller than 1 , as shown in fig4 which illustrates the results of our measurements , and prove that the measured parameter is the electrode polarization impedance . a device of the invention is illustrated with reference to fig5 which illustrates a probe according to the invention . fig6 which illustrates a professional version of a probe for hospital or clinical use ; as shown in fig2 a probe comprises an elongated member 21 , made of non - conductive material at the end of which there are provided two ring - shaped electrodes 25 , which are connected via wires 24 to the outside . at the end of the probe , there can be provided a temperature sensor 23 which is also connected via a wires 26 to the outside of the probe . the procedure is that each morning a measurement is carried out , during about 10 - 30 seconds , with the data being stored in a microprocessor , and which data are processed according to existing software algorithms , providing a clear indication of the various phases of the cycle . the combined data provides reliable means for recognizing fertile and infertile phases of the cycle . a typical graph of such a measurement of the two parameters is given in fig8 . according to a simplified embodiment of the invention there is provided a system for domestic use . this comprises a probe of the invention , integrated with a microprocessor which will be used to compute daily measurements and to indicate via three difference leds or lcd display : ( 1 ) a signal indicating that ovulation is approximately three days away ; ( 2 ) a signal indicating the most fertile period ( day ) of ovulation ; ( 3 ) a signal the start of the infertile phase after ovulation . if leds are used they are preferably of different color . the entire device is in the form of a compact integrated apparatus housed in the handle of the probe , provided with such indication means . in fig6 is a calibration button , 62 a daily button , 63 the two test electrodes , 64 temperature electrodes and 65 a connector for the p . c . computer ; in fig7 is a calibration and daily button , 72 are the respective yellow , red and green leds , 73 are the two test electrodes and 74 the temperature electrodes , 75 being a connector to the p . c . computer . a typical curve obtained by means of such a device is shown in fig9 but this is not displayed and its use is to actuate at the appropriate time the correct led or any kind of indication -- numerical , bar graph -- which can be displayed on an lcd display . output signals of this device will not exceed 15 mvolts peak to peak ac in a frequency range of 10 khz to 100 khz in constant current which does not exceed 50 μamp between the two stainless steel electrodes . the batteries of this apparatus can be in the range of 1 . 5 - 6 volts dc . algorithm software : the software of the device is based upon statistical measurements which were conducted on a test group of subjects . automatic levelling procedure is a part of the software . this is in order to eliminate the differences between users . a drop of 10 - 15 % from the baseline will give indication of at least 72 hours before ovulation . in order to strengthen this early warning , software is calculating in parallel the rhythm method and will display first indications , whatever comes first as an early warning . after confirmation of the two parameters , the display signal will indicate this . after the software has recognized the nadir day , it will start to in after dictate that fertile phase is starting to pass . in parallel , software is used to check temperature changes . when a count of three days of rising temperature is indicated and at the same time the polarization impedance is on a constant rise , then on the fourth day the indication signal of fertile phase will turn off and a new signal indicating infertile phase will start . ______________________________________legend to fig1 no . device circuit use______________________________________101 op . amp oscillator amplifier102 capacitor oscillator timing103 resistor oscillator timing104 resistor oscillator gain105 capacitor oscillator timing106 resistor oscillator timing107 resistor oscillator gain108 resistor oscillator output current control109 capacitor oscillator d . c . reject110 inp . probe z sensor sensor111 capacitor a . c . amp . high pass112 resistor a . c . amp . high pass113 resistor a . c . amp . gain114 resistor a . c . amp . gain115 op . amp a . c . amp . amplifier116 capacitor rectifier cir . coupling117 resistor rectifier cir . coupling118 op . amp rectifier cir . amplifier119 diode rectifier cir . rectification120 capacitor rectifier cir . averaging121 resistor rectifier cir . averaging122 nic resistor temp . meas . temperature sensor123 resistor m . f . temp . meas . reference resistor124 op . amp temp . meas . amplifier125 resistor temp . meas . zero temp . set . 126 resistor temp . meas . zero temp . set . 127 dig . interface i / o port communication128 dig . interface alu and display central control129 a / d converter and mpxr converter of z . t . to dig . 130 vagina female sensed device______________________________________