A mammography system including a compression device, comprising two compression members to compress a breast, a sensor to sense the pressure exerted by the breast on one of the members and/or a device to determine the distance between the two members, an X-ray image acquisition system, means to adjust an initial position of the members. The system further comprises means to monitor variations in pressure and/or variations in thickness relative to their initial value, for an estimation of the risk of breast movement. The system further comprises means to present the user with information signaling breast movement, in relation to the estimation.