[Antithyroid drug therapy in pregnancy. An indication for pregnancy interruption based on fetal indications?]

Antithyroid drugs can pass the placenta, in contrast to thyroid hormones. Therefore, their application in pregnancy carries the potential risks of teratogenic effects and foetal hypothyroidism. The actual danger to the foetus, however, is controversial. The history of a hyperthyroid patient treated with carbimazole and referred for termination of pregnancy in the 8th week of gestation gave rise to review the literature in order to elucidate the foetal risks. Data of 278 pregnant women treated with imidazole derivatives (group I) and 192 women, who received thiouracil derivatives (group II) during pregnancy, were found in the literature. The rates of foetal malformations and foetal goitre in group I were 3.6% and 3.2%, respectively. In group II the corresponding rates were 3.6% for foetal malformation and 7.8% for foetal goitre. From these figures we conclude that antithyroid therapy in pregnancy does not warrant termination of pregnancy for foetal reasons if there is meticulous control of maternal thyroid metabolism.