Thyroid Cancer Treatment Pregnancy

Thyroid cancer is most common in people between the ages of 20 and 40, and it’s much more common in women than men.

Therefore, it’s not surprising that some of the new thyroid cancer patients diagnosed each year are pregnant. In fact, thyroid cancer is the second most frequent form of cancer diagnosed during pregnancy.

Researchers have found that there may be a direct relationship between pregnancy and thyroid cancer, due to the 20–30 percent growth of the thyroid during pregnancy. This growth leads to the development of new — and possibly cancerous — cells.

Although dealing with pregnancy and thyroid cancer at the same time can feel overwhelming, effective treatment can lead to a healthy pregnancy and birth.

Timing Treatment for the Thyroid in Pregnancy

Fortunately for those facing both pregnancy and thyroid cancer, the most common forms of thyroid cancer are very slow growing. If thyroid cancer is discovered in the course of a pregnancy, the patient and her doctor have the option of adjusting treatment so it can be done with the least impact on the fetus.

Patients and their doctors may even consider delaying treatment until after childbirth, under the following conditions:

  • Other aspects of the pregnancy increase surgery risks.
  • The cancer does not seem to be aggressive and has not spread.
  • The cancer is papillary or follicular.
  • The patient has no history of thyroid disease.
  • The tumor is small.

When thyroid cancer surgery must be conducted during pregnancy, it is usually performed in the second trimester, between months four and six.

Treating Cancer During Pregnancy — Thyroid Hormone Levels

During pregnancy, thyroid functions are very important. Even mild hypothyroidism can cause serious problems, such as trouble with the baby’s mental development and premature birth.

Controlling levels of thyroid hormone (T4) and thyroid stimulating hormone (TSH) will promote a healthy outcome for both baby and mother. Treatment with thyroxine is sometimes recommended to keep TSH at a safe level. Patients will likely be tested every one to two months to make sure they’re in the appropriate range.

Post-Pregnancy Thyroid Cancer Follow Up

Radioactive iodine treatment (RAI) is frequently used after thyroid cancer surgery to eliminate remaining thyroid cancer cells. It’s part of the aggressive plan recommended for women who delayed treatment due to pregnancy.

However, RAI can’t be used during pregnancy because it could damage the fetus’ developing thyroid gland. Women who are breastfeeding should not receive RAI. Since active breasts are more likely to concentrate the radioactive iodine, some experts recommend waiting months after breastfeeding before using RAI.

Patients with questions about breast-feeding, pregnancy and thyroid cancer should discuss all their treatment choices with their healthcare providers.


Johns Hopkins Thyroid Tumor Center staff. (ND). Thyroid cancer answers. Retrieved April 5, 2010, from the Web site:

Drucker, D. (2005). Pregnancy. April 5, 2010, from the My Web site:

Perrino, M. et al. (2007). Thyroid cancer and pregnancy: Clinical outcome and time of diagnosis in a series of 94 women. Retrieved April 5, 2010, from the Endocrine Abstracts Web site: