Thyroid cancer seems to be rare during pregnancy. No endocrine association between maternal hormonal changes and thyroid cancer has been found.The well differentiated subtypes (papillary and follicular) have a female predominance, often present with an indolent, asymptomatic course during pregnancy), and represent a significant proportion of all cancers in women of childbearing age. Tumor types are similar to non-pregnant patients. Most pregnant patients present with well differentiated, localized disease and extensive staging investigations are not indicated. Radioactive iodine for diagnosis is contraindicated during pregnancy. Decisions regarding the use of radiological investigations must take into account the age of the fetus and the estimated dose of fetal radiation exposure.
Therapeutically, lobectomy with cervical node dissection can be performed. Radioactive iodine should be avoided, and chemotherapy is not effective. Surgery remains treatment of choice for well differentiated thyroid cancer. Due to the relatively indolent course but potential impact on long term survival, therapy during pregnancy can be tailored to the stage of pregnancy. For those presenting in the first trimester, surgery and general anaesthesia can be delayed until the second trimester to reduce the risks associated with surgery to the fetus. For those patients who present in the later stages of pregnancy with a well-differentiated tumor, surgery can usually be delayed safely until the post partum period. Radioiodine therapy is contraindicated during pregnancy as it can cross the placenta and cause fetal hypothyroidism and cretinism. It has been suggested that women receiving radioiodine not become pregnant for at least 12 months post therapy to ensure elimination of I-131, and confirm disease remission. This should help avoid the higher miscarriage rate seen in the first few months after radioiodine treatment. A recent study suggested that even shorter period (7 women conceived within 6 months after the last administration of I 1311) does not result in demonstratable side effects in subsequent pregnancies.