The ovaries are responsible for not only providing the seeds of reproduction – the eggs – but also secreting female hormones to maintain female characteristics and pregnancy. However, there are times when the ovaries may be sick and persist in their work, such as when ovarian cysts are combined with pregnancy. This can be tricky to deal with and requires consideration of both the pregnant woman and the fetus. Therefore, it is recommended that women who are planning to get pregnant should have a thorough examination before pregnancy] The coexistence of ovarian tumor and pregnancy is not rare, occurring about once in every 100 to 8000 pregnancies, and the majority of them are benign tumors, accounting for 95-98%. The reason why it is taken seriously is that it is confusing to deal with and concerns both the mother and the child. The most common benign ovarian tumors associated with pregnancy are mature cystic teratomas and plasmacytic (or mucinous) cystadenomas. 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 process of pregnancy not only reproduces offspring but is also a natural enemy of ovarian tumors, but it is clearly absurd to prevent cancer through pregnancy. Conversely, ovarian tumors are also enemies of pregnancy and can affect pregnancy in the 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. The physiological changes of the body during pregnancy may also affect the ovarian tumor and develop toward an unfavorable situation. The pelvic cavity is filled with blood during pregnancy and the blood supply to the ovary increases, so the tumor can grow rapidly; during pregnancy, the increase of the uterus and the change of the position can cause the ovarian tumor to twist; and the extrusion during delivery may cause the tumor to rupture. Moreover, the enlarged uterus during pregnancy often makes ovarian tumors not easy to be detected and delays the diagnosis and treatment of tumors. Therefore, when dealing with pregnancy and cancer, it is often a dilemma. 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 is also required. Secondly, if it is decided to operate during pregnancy, a comprehensive exploration of 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 benign and malignant nature of the tumor, and comprehensive exploration and removal of suspicious tissues should be sent to rapid pathological examination to determine the preliminary diagnosis and histological category, which is a matter for doctors and not to be described too much. Finally, 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 blood concentration when you have a tumor, such as CA125, CA199, CEA, AFP, etc.). In general, ovarian cysts over 5 cm in diameter only need to be treated if you are not pregnant, but for women who are planning to get pregnant, the criteria are slightly stricter, tentatively 4 cm, and even if the contents of the mass are liquid (called a cyst), surgery should be performed, and minimally invasive laparoscopic surgery is best. However, even if the mass is less than 4 cm in diameter, but has a solid component that does not disappear after several examinations, it should be treated before pregnancy to avoid the risk of tumor growth after pregnancy. In conclusion, it is better to check and exclude ovarian tumor before pregnancy, to defuse the time bomb and to pass the pregnancy period safely and happily.