The term immature teratoid fetus becoming mature refers primarily to the reversal of the malignancy of an immature teratoma. Teratomas are usually categorized into two types: mature teratomas, which are benign, and immature teratomas, which are malignant. Ovarian immature teratomas are highly malignant. Malignant germ cell tumors of the ovary account for 5-15% of ovarian malignancies. Their prognosis has been greatly improved by treatment with combination chemotherapy regimens. The survival rate has increased from 10-20% in the past to more than 95%. Immature teratomas that recur have the potential to transform from immature to mature, which is a biological behavior of benign transformation. Because of the recurrence of the disease, if diagnosed with immature teratoma, patients should pay attention to regular medical checkups after treatment, relax and actively cooperate with the doctor’s treatment plan, and if they feel unwell, it is recommended to consult the doctor in time.