Embodiments for providing a plurality of slice images are disclosed. In one embodiment, by way of non-limiting example, an ultrasound system comprises: an ultrasound data acquisition unit configured to transmit and receive ultrasound signals to and from a target object to thereby output ultrasound data; and a processing unit configured to form volume data based on the ultrasound data, set a reference slice, a reference point and a window on the volume data based on input information of a user and set a sagittal view for measuring a thickness of a nuchal translucency (NT) of a fetus on the volume data.