The invention relates to a magnetic resonance imaging system (10), the system comprising a magnetic resonance imaging device (12) for acquiring data from a moving subject (14), especially a fetus or a part of said fetus; and an image generator (30) for generating an image of said moving subject (14), wherein the magnetic resonance imaging device (12) is configured to acquire the data from the subject (14) at different positions of said subject (14) with respect to a magnetization direction B0, utilizing the movement of the subject (14); and wherein the image generator (30) is configured to —determine the position and/or orientation of said subject (14) during the respective data acquisition; —reconstruct phase images from the acquired data; and —generate a susceptibility map based on the reconstructed phase images. The invention further relates to a corresponding method for generating an image of the subject (14).