Prenatal treatment of fetal hypothyroidism: is there more than one option?

Following the diagnosis of fetal goitre at 22 and 24 weeks' gestation in two hyperthyroid pregnant women who underwent treatment with 400-500 mg of propylthiouracil in the first weeks of pregnancy, a total of seven fetal blood samplings were performed to evaluate thyroid function before and after the initiation of two different treatment regimens. L-Thyroxine (600 micrograms) was injected five times intra-amniotically in one woman and continuous maternal administration of the thyroid analogue 3, 5, 3'-triiodothyroacetic acid (Triac) was attempted in the other. Normalization of fetal thyroid function and reduction of fetal goitre were achieved in both fetuses and transplacental passage of Triac was indirectly demonstrated by high levels of free triiodothyronine in fetal blood. In cases of fetal hypothyroidism, direct or indirect prenatal therapy can be adopted successfully and safely.