PCO refers to polycystic changes in the left ovary, the cause of which is not particularly clear, and is mostly considered to be related to genetics or lifestyle. Polycystic change of the left ovary is generally described by ultrasound as a very large number of small follicles on the ovary, and an ultrasound showing more than 12 small follicles in a single section is called polycystic change of the ovary. If ovarian polycystic changes are accompanied by menstrual abnormalities, weight gain, and acne, then it may be polycystic ovary syndrome, which may affect your health and fertility and requires prompt treatment. Simple polycystic ovarian changes with no abnormalities usually do not require special treatment, while polycystic ovary syndrome is recommended to consult a doctor for standardized treatment.