Graves' disease is one of the major causes of hyperthyroidism, which is due to an overactive thyroid gland.
In cases of Graves' disease in pregnancy, poorly controlled hyperthyroidism exposes the woman to an increased risk of pre-eclampsia, i.e. high blood pressure and complications, as well as heart failure. This also exposes the unborn child to an increased risk of intrauterine growth retardation, fetal death and premature birth, hyperthyroidism, and mental retardation.
Surgery in pregnancy carries a number of risks and is reserved for situations where a synthetic antithyroid is not desirable. Radioactive iodine should be ruled out as a treatment for pregnant women.
During pregnancy, synthetic antithyroid drugs are the treatment of choice, but they cross the placenta and hinder the functioning of the fetal thyroid, which means the minimum effective dose should be used.
In the first trimester, propylthiouracil is the drug of choice because malformations appeared to be less severe and less common than with carbimazole or thiamazol. In the second and third trimesters, if it is not possible to halt antithyroid treatment, the risk of hepatic damage associated with propylthiouracil is a reason to replace it with carbimazole or thiamazol.
When a beta-blocker is justified to relieve symptoms of hyperthyroidism, propranolol is the drug of choice, to be used for as short a time as possible.
©Prescrire 1 July 2017
"Graves' disease during pregnancy. Treatment is problematic" Prescrire Int 2017; 26 (184): 188-192. (Pdf, subscribers only).