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Pregnancy and Thyroid Disease

© Keri

In the previous article, we discussed the potential effects of hypothyroidism on the intellectual development of the child. But just how common is thyroid disease in pregnancy? According to the Thyroid Foundation of Canada, thyroid disease occurs in 1-2 percent of women of child-bearing age. Thyroid disease is not uncommon in pregnancy and post partum, the time immediately after delivery. In fact, some sources speculate that many cases of post partum depression may in fact be due to thyroiditis, an inflammation of the thyroid.

Some sources recommend that all pregnant patients be screened for possible thyroid disease in the first trimester of pregnancy. Others argue that with the incidence of thyroid disease in pregnancy of less than 1% such testing is not cost effective. Regardless, all sources agree that women exhibiting signs of thyroid disease should be closely monitored during pregnancy. Women with a history of miscarriage or unexplained infertility should also be tested before and during her pregnancy.

The types of thyroid disease manifesting during pregnancy tend to be autoimmune, meaning that the body produces antibodies that fight against it’s own tissue instead of an invading virus or bacteria. Both Hashimotos Thyroiditis and Graves’ Disease are autoimmune disorders. Women who have been previously treated may experience a relapse during or immediately after pregnancy requiring treatment. Rarely, other thyroid problems including nodules or cancer are sometimes be first detected during pregnancy.

Women with existing hypothyroidism, underactive thyroid, may need an increase in their thyroid hormone replacement during pregnancy. Thyroxine, synthetic T4 replacement, is considered safe to take during pregnancy and breast-feeding. It is the recommended therapy for hypothyroidism according to the American Academy of Clinical Endocrinologists.

Hyperthyroidism in pregnancy presents unique concerns. Many of the signs and symptoms of thyroid disease are common in pregnancy, i.e., tiredness, difficulty sleeping, hot flashes, etc. Diagnosing and treating hyperthyroidism presents more of a challenge due to the inability to use radioactive iodine for scan or treatment during the pregnancy. The exposure to RAI can impact fetal development and have the same potential effect on the fetal thyroid as the mother’s. But, keep in mind that many normal infants have been born in this situation.

The treatment of choice during pregnancy is anti-thyroid drugs. Usually, propylthiouracil (PTU) since it is felt to be less able to cross the placenta and effect the fetus. The goal is to treat with the lowest dose possible to control the hyperthyroidism. Again, TSH levels should be closely monitored. Pregnancy can cause a remission of Graves’ Disease. However, there may be a recurrence immediately after delivery.

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