The coexistence of ovarian tumors and pregnancy is not really common, especially in malignant tumors. The reason why it is taken seriously is that it is tricky to manage and concerns both the mother and the child. The incidence of ovarian tumors in conjunction with pregnancy varies widely from 1:81 to 1:8000 pregnancies, with benign tumors accounting for 95% to 98% and malignant tumors accounting for only 2% to 5%. Benign ovarian tumors include mature cystic teratoma and plasmacytic (or mucinous) cystadenoma, while malignant ovarian tumors are mainly asexual cell tumors and plasmacytic cystic adenocarcinoma. It can be said that the ovarian ovulation process, which controls a woman’s monthly menstruation, is one of the culprits of ovarian destruction, and pregnancy is one of the best protections for the ovaries. During the months of pregnancy, the ovaries stop ovulating and recuperate. Thus, the pregnancy process not only reproduces offspring, but is also a natural enemy of ovarian tumors (but preventing cancer through pregnancy is obviously absurd). In turn, ovarian tumors are enemies of pregnancy and can affect pregnancy in early, middle and late stages of pregnancy. In early pregnancy, the tumor may be embedded in the pelvic cavity, causing abnormal uterine position or stimulating uterine contraction, thus inducing spontaneous abortion. In late pregnancy, if the tumor is large and squeezes the uterus, it may cause abnormal fetal position and prevent the fetal head from entering the pelvis; if the tumor is low, it may obstruct the birth canal and cause obstructed labor. What’s more, the physiological changes of the body during pregnancy can also affect ovarian tumors and develop toward an unfavorable situation. If the tumor is malignant, it may spread; during pregnancy, the increase of uterus volume and position may cause ovarian tumor to twist; and the extrusion during delivery may cause tumor rupture. Moreover, the enlargement of the uterus during pregnancy often makes ovarian tumors not easy to be detected and delays the diagnosis and treatment of tumors. Therefore, it is often a dilemma when dealing with pregnancy and cancer. The dilemma is whether the pregnancy should be terminated or not. Will the prognosis of the tumor be affected if the pregnancy continues until the fetus is viable? How will the tumor affect the fetus? What are the risks to the fetus that would result from treatment of the tumor? What is the likelihood of future pregnancies after termination of the current pregnancy? When is the best time to operate? When is the best time to operate? It is necessary for the doctor to consult with the patient and her family, weigh the pros and cons and decide the treatment plan. First of all, it is important to pay attention to the pelvic masses found during pregnancy without delaying the diagnosis of malignancy. Specific principles:① For ovarian masses combined with pregnancy, if they are less than 5 cm in diameter and gradually shrink on examination, they can be considered physiological cysts and do not need to be treated; if the history and examination are highly suspicious of endometriotic cysts, they can also be left untreated for the time being, especially in elderly patients who are well pregnant, because the large amount of progesterone secreted during pregnancy will inhibit their growth; ② If the masses are more than 5 cm in diameter , then laparoscopic surgery or caesarean section should be performed around 16 weeks of pregnancy, regardless of complications such as torsion. Only by performing surgery in a timely manner can complications be avoided and malignant conditions be detected in a timely manner. It is generally accepted that surgery in the middle of pregnancy is less likely to induce miscarriage compared to early pregnancy and that anesthetic drugs and other drugs have less impact on fetal development. (iii) If the mass is hard, nodular, fixed or bilateral, especially if malignancy cannot be excluded, caesarean section should be performed regardless of the gestational age. If it is complicated by tumor torsion, rupture or infection, or accompanied by acute abdominal pain, nausea and vomiting, or even shock, immediate surgery should also be performed. Secondly, if it is decided to operate during pregnancy, a comprehensive exploration of the pelvic and abdominal cavity is needed during the operation, and the resected mass should be initially judged by the naked eye whether it is malignant or not, and sent to frozen section for rapid pathology to determine the benignity and malignancy of the tumor, and a comprehensive exploration and removal of suspicious tissues should be sent to rapid pathological examination to determine the preliminary diagnosis and histological category. This is the basis for choosing the scope of surgery, which is of course the doctor’s business. 1. If the lesion is confined to one ovary, with intact envelope and no metastatic implantation manifestation, which is the so-called clinical stage Ia; if the lesion is of low malignancy, unilateral adnexal (i.e. fallopian tube ovary) resection can be performed and the contralateral ovary biopsy. Pregnancy can be maintained until full term. 2. If the lesion is beyond stage Ia epithelial ovarian cancer, a full-scale surgery, i.e., tumor cytoreduction, should be performed. The consideration of pregnancy is obviously secondary at this point. For malignant germ cell tumors, even if the lesion is beyond the ovary, only the diseased ovary and metastases can be removed, preserving the pregnant uterus and the contralateral ovary. 4.If the ovarian cancer is metastatic from malignant tumors in the kidney, gastrointestinal tract, breast, etc., the prognosis for mother and child is poor. Maintaining the pregnancy until full term may comfort the mother for the rest of her life. For tumors, unless there are complications, treatment may not be necessary. You can see how difficult it is to deal with ovarian tumors found only after pregnancy! Therefore, for women who are planning to get pregnant, a thorough examination before pregnancy is necessary. The items include at least a pelvic ultrasound and, if necessary, a blood test for tumor surface markers (certain specific substances that increase in concentration in the blood when a tumor is present, such as CA125, CA199, CEA, AFP, etc.). As a rule, ovarian cysts over 5 cm in diameter need to be treated if there is no pregnancy, but for women who are planning to get pregnant, the criteria are stricter, tentatively set at 4 cm, and even if the contents of the mass are fluid (called cyst), surgery should be performed, and laparoscopic minimally invasive surgery is best. Or even if the diameter is less than 4 cm, but the tumor has a solid component and does not disappear after several examinations, it should be treated before pregnancy to avoid the danger of tumor growth after pregnancy. It is the best policy to remove the time bomb before pregnancy and eliminate the tumor before the scourge occurs.