A system for determining a fertile window of a woman, the system comprising: - a contact sensor unit for providing a signal in contact with the woman, wherein the signal is indicative of respiration of the woman, and - a processing unit for processing the signal to obtain a biomechanical parameter indicative of respiration, wherein the processing unit is configured to determine the fertile window of the woman based on a change in the obtained biomechanical parameter, and characterized in that the contact sensor unit comprises at least one of: i) a bio-impedance sensor configured to be attached to the thorax of the woman, wherein the bio-impedance sensor is configured to obtain a signal indicative of a tidal volume, wherein preferably the processing unit is configured to determine a minute volume based on a product of tidal volume and respiratory rate, ii) an electromyography sensor configured to determine the electrical activity of muscles, preferably of intercostal parasternal muscles, wherein the processing unit is configured to determine a respiratory drive from the determined electrical activity, and iii) at least one of an inductance and a stretch sensor for measuring an expansion of the thorax of the woman, wherein the processing unit is configured to determine a respiration rate based on the measured expansion of the thorax. - a contact sensor unit for providing a signal in contact with the woman, wherein the signal is indicative of respiration of the woman, and - a processing unit for processing the signal to obtain a biomechanical parameter indicative of respiration, wherein the processing unit is configured to determine the fertile window of the woman based on a change in the obtained biomechanical parameter, and characterized in that the contact sensor unit comprises at least one of: i) a bio-impedance sensor configured to be attached to the thorax of the woman, wherein the bio-impedance sensor is configured to obtain a signal indicative of a tidal volume, wherein preferably the processing unit is configured to determine a minute volume based on a product of tidal volume and respiratory rate, ii) an electromyography sensor configured to determine the electrical activity of muscles, preferably of intercostal parasternal muscles, wherein the processing unit is configured to determine a respiratory drive from the determined electrical activity, and iii) at least one of an inductance and a stretch sensor for measuring an expansion of the thorax of the woman, wherein the processing unit is configured to determine a respiration rate based on the measured expansion of the thorax. i) a bio-impedance sensor configured to be attached to the thorax of the woman, wherein the bio-impedance sensor is configured to obtain a signal indicative of a tidal volume, wherein preferably the processing unit is configured to determine a minute volume based on a product of tidal volume and respiratory rate, ii) an electromyography sensor configured to determine the electrical activity of muscles, preferably of intercostal parasternal muscles, wherein the processing unit is configured to determine a respiratory drive from the determined electrical activity, and iii) at least one of an inductance and a stretch sensor for measuring an expansion of the thorax of the woman, wherein the processing unit is configured to determine a respiration rate based on the measured expansion of the thorax.