OBJECTIVE: Previous studies recommend the discontinuation of antithyroid drug (ATD) therapy during pregnancy in women with well-controlled Graves' hyperthyroidism (GH). In this study, we investigated whether this termination of ATD therapy during pregnancy is beneficial in terms of postpartum GH recurrence. DESIGN: A nonrandomized, retrospective study. PATIENTS: Sixty-five pregnant GH patients treated with maintenance doses of ATDs were assigned into two groups: ATD therapy was discontinued before delivery in Group 1, but continued during pregnancy and after delivery in Group 2. MEASUREMENTS: The prevalence of postpartum recurrence or exacerbation of GH within 1 year after delivery was examined. Serum T4, T3 TSH, and TSH receptor antibody levels were measured. RESULTS: In Group 1, 70.8% (17/24) of patients suffered a recurrence of GH within 1 year after delivery. In contrast, a postpartum exacerbation of GH was observed in only 29% (12/41) of patients in Group 2 (P < 0.01). Both exacerbations and recurrences of GH appeared primarily within 4-6 months after delivery. Apparent neonatal hypothyroidism and malformations were not observed in the offspring of either group. CONCLUSION: Continuing antithyroid drug therapy throughout pregnancy prevents postpartum recurrence of Graves' hyperthyroidism without resulting in neonatal hypothyroidism or malformations.
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