An ultrasound diagnosis apparatus, comprising: a probe configured to transmit ultrasound signals to an ovarian region of an object and receive echo signals reflected from the ovarian region; a processor configured to: - obtain a three-dimensional ultrasound image including the ovarian region based on the echo signals; and - detect, based on at least one parameter used for extracting a particular oocyte, a plurality of candidate ovarian follicles from which mature oocytes are more likely to be extracted in the three-dimensional ultrasound image, CHARACTERISED IN THAT the processor is further configured to: - register a two-dimensional ultrasound image corresponding to a first cross-section of the ovarian region to the three-dimensional ultrasound image; and - guide, based on a result of the registering, a position of at least one candidate ovarian follicle from which an oocyte is to be extracted in the two-dimensional ultrasound image, wherein the ultrasound diagnosis apparatus further comprises: a display configured to display information for guiding the position of the at least one candidate ovarian follicle; and an oocyte extractor configured to extract an oocyte from the at least one candidate ovarian follicle. a probe configured to transmit ultrasound signals to an ovarian region of an object and receive echo signals reflected from the ovarian region; a processor configured to: - obtain a three-dimensional ultrasound image including the ovarian region based on the echo signals; and - detect, based on at least one parameter used for extracting a particular oocyte, a plurality of candidate ovarian follicles from which mature oocytes are more likely to be extracted in the three-dimensional ultrasound image, - obtain a three-dimensional ultrasound image including the ovarian region based on the echo signals; and - detect, based on at least one parameter used for extracting a particular oocyte, a plurality of candidate ovarian follicles from which mature oocytes are more likely to be extracted in the three-dimensional ultrasound image, the processor is further configured to: - register a two-dimensional ultrasound image corresponding to a first cross-section of the ovarian region to the three-dimensional ultrasound image; and - guide, based on a result of the registering, a position of at least one candidate ovarian follicle from which an oocyte is to be extracted in the two-dimensional ultrasound image, - register a two-dimensional ultrasound image corresponding to a first cross-section of the ovarian region to the three-dimensional ultrasound image; and - guide, based on a result of the registering, a position of at least one candidate ovarian follicle from which an oocyte is to be extracted in the two-dimensional ultrasound image, wherein the ultrasound diagnosis apparatus further comprises: a display configured to display information for guiding the position of the at least one candidate ovarian follicle; and an oocyte extractor configured to extract an oocyte from the at least one candidate ovarian follicle. a display configured to display information for guiding the position of the at least one candidate ovarian follicle; and an oocyte extractor configured to extract an oocyte from the at least one candidate ovarian follicle.