Management of overt hypothyroidism during pregnancy

Overt hypothyroidism is a common endocrine disorder affecting 1-2% of women of reproductive age. Optimizing treatment in pregnant women with overt hypothyroidism can reduce adverse fetal and maternal outcomes. Ideally, women who are known to have a history of hypothyroidism or those with risk factors for becoming hypothyroid, should have adequate preconception care to ensure euthyroidism from the onset of pregnancy, with a TSH target of below 2.5mIU/L. On women who are already on levothyroxine, an empirical dose increase of 30-50% as soon as pregnancy is confirmed may be considered. During pregnancy, levothyroxine doses should be titrated against TSH, which have trimester-specific ranges. In women who are known to be hypothyroid but are inadequately treated, we recommend a doubling of levothyroxine dose on at least three days a week to rapidly achieve euthyroidism. In newly diagnosed overt hypothyroidism in pregnancy, starting doses of either 100 or 150 mg daily may be considered safe.