The invention relates to a system, method and corresponding computer program for unobtrusively determining a fertile window. In particular, it relates to a wearable system such as integrated in a bra for supporting personalized prediction of the fertile window for a planned parent-hood purpose. The system (1) comprises a contact sensor unit (10) for providing a signal in contact with the woman, wherein the signal is indicative of respiration of the woman, and a processing unit (20) for processing the signal to obtain a parameter indicative of respiration, wherein the processing unit (20) is configured to determine the fertile window of the woman based on a change in the obtained parameter. The system (1) allows a reliable unobtrusive determination of a fertile window of a women.
