Thyroid function should be assessed in women with hyperemesis gravidarum. Women known to have Graves' disease may decide on definitive treatment of their condition prior to becoming pregnant. If Graves' disease is diagnosed during pregnancy, it is important to use the smallest dose of antithyroid drugs by reviewing regularly to maintain maternal concentrations of free thyroid hormone and thyroid-stimulating hormone within their respective normal ranges. This is to avoid fetal hypothyroidism and goiter. Most recommend that carbimazole should be discontinued 4 weeks before the expected date of delivery to avoid any possibility of fetal hypothyroidism at the time of maximum brain development. If subtotal thyroidectomy is necessary because of poor drug compliance or hypersensitivity, it is most safely performed in the middle trimester. Radio-iodine is contraindicated because it invariably induces fetal hypothyroidism. If antithyroid agents are given postdelivery, breast feeding is not precluded. As propylthiouracil is excreted less in breast milk, it is preferable to use this agent at the lowest effective dose. Patients already receiving carbimazole need not normally change provided that the daily dose is 20 mg or less. In dire circumstances when patients are not responding to conventional therapy plasmapharesis should be considered (Derkson, §1M 1984).
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