PURPOSE: to evaluate the influence of hyperthyroidism during pregnancy and the necessity of changing antithyroid drug dose in this period and after delivery. METHODS: prospective evaluation of clinical and laboratorial findings of thirteen pregnancies in eleven pregnant women with hyperthyroidism due to Graves' disease. These women were evaluated through TSH and serum free T4 at each trimester or four weeks after setting thionamide dosage. The goal was to maintain free T4 in the superior third of the normal range using the lowest possible thionamide dose. RESULTS: the mean age at the beginning of the pregnancy was 31.1 years (23 to 41). The mean dosage of thionamide was reduced in eight pregnancies (69.5%) and, in two, the drug was discontinued. Before pregnancy, mean propylthiouracil dose was 400 mg/day (200-900) and mean methimazole dose was 45 mg/day (20-60). After delivery, antithyroid drug dose was 200 and 30 mg/day, respectively. One patient presented premature labor (at 36 weeks) and another, a newborn small for gestational age (2.000 g at 38 weeks). There was one stillborn. There were no miscarriages or congenital anomalies. After labor, antithyroid drug dose was increased in seven patients and in the others the dose was maintained. CONCLUSIONS: we suggest close follow-up of pregnant women with hyperthyroidism and progressive reduction of thionamide dose during pregnancy to avoid maternal hypothyroidism and its consequences to fetal development. After labor, these women must be evaluated regarding their thyroid function because hyperthyroidism can worsen. Thionamide use is safe for the patients and their offspring.
Pregnancy complications; Hyperthyroidism; Graves' disease
