(1) Thyroid cancer was diagnosed before pregnancy and was treated. There was no significant difference in the rate of disease recurrence in patients with thyroid cancer who survived treatment without disease, with or without pregnancy. (2) Thyroid cancer was diagnosed before pregnancy and has not been treated. Pregnancy may cause an increase in (untreated) PMTC. (3) Thyroid cancer was diagnosed during pregnancy. General: It is not possible to give a definitive answer as to whether pregnancy accelerates the progression of thyroid cancer. For those diagnosed before pregnancy and in disease-free survival after treatment, there is more agreement that pregnancy has no effect on the disease. For those diagnosed prior to pregnancy but not treated, the only observation in a small sample suggests that pregnancy may cause further growth of PTMC. For patients with thyroid cancer diagnosed during pregnancy or within 1 to 2 years after delivery, it is controversial whether pregnancy affects long-term prognosis. Does pregnancy affect the treatment options for thyroid cancer? Surgery is one of the most important treatments for thyroid cancer. Surgery during the third trimester may affect fetal organogenesis and cause spontaneous abortion, and surgery during the seventh to ninth trimester may lead to preterm delivery. RAI, another treatment for thyroid cancer, cannot be used during pregnancy because pregnancy is an absolute contraindication to radionuclide screening and treatment. Factors affecting pregnancy in thyroid cancer: Abnormal states of thyroid function such as hypothyroidism, subclinical hypothyroidism, hyperthyroidism or subclinical hyperthyroidism may occur during surgery, iodine therapy and TSH suppression therapy for thyroid cancer. Studies have shown that these states of thyroid dysfunction (with the exception of subclinical hyperthyroidism) have the potential to affect pregnancy and offspring. Hypothyroidism can affect menstruation and ovulation, reduce pregnancy rates, increase the incidence of pregnancy and perinatal complications, and lead to impaired growth and development of the offspring; subclinical hypothyroidism is also associated with increased miscarriage rates, increased risk of pregnancy and perinatal complications, and impaired mental development of the offspring; hyperthyroidism can lead to abnormal menstruation, increased miscarriage rates and pregnancy and perinatal complications, and can also affect the fetus due to high T4 levels in late pregnancy. Hyperthyroidism can also affect the normal feedback function of the pituitary-thyroid axis in the fetus due to high T4 levels in late pregnancy.