Preconception Management of Thyroid Dysfunction

Onyebuchi E. Okosieme; Ishrat Khan; Peter N. Taylor


Clin Endocrinol. 2018;89(3):269-279. 

In This Article

Abstract and Introduction


Uncorrected thyroid dysfunction in pregnancy has well-recognized deleterious effects on foetal and maternal health. The early gestation period is one of the critical foetal vulnerability during which maternal thyroid dysfunction may have lasting repercussions. Accordingly, a pragmatic preconception strategy is key for ensuring optimal thyroid disease outcomes in pregnancy. Preconception planning in women with hypothyroidism should pre-empt and mirror the adaptive changes in the thyroid gland by careful levothyroxine dose adjustments to ensure adequate foetal thyroid hormone delivery in pregnancy. In hyperthyroidism, the goal of preconception therapy is to control hyperthyroidism while curtailing the unwanted side effects of foetal and maternal exposure to antithyroid drugs. Thus, pregnancy should be deferred until a stable euthyroid state is achieved, and definitive therapy with radioiodine or surgery should be considered in women with Graves' disease planning future pregnancy. Women with active disease who are imminently trying to conceive should be switched to propylthiouracil either preconception or at conception in order to minimize the risk of birth defects from carbimazole or methimazole exposure. Optimal strategies for women with borderline states of thyroid dysfunction namely subclinical hypothyroidism, isolated hypothyroxinaemia and thyroid autoimmunity remain uncertain due to the dearth of controlled interventional trials. Future trial designs should aspire to recruit and initiate therapy before conception or as early as possible in pregnancy.


Thyroid disorders are common in women of reproductive age.[1] Overt thyroid disease carries an increased risk of adverse pregnancy outcomes including miscarriages, stillbirths and neuro-intellectual impairment in the offspring.[2–4] These adverse events also occur, albeit to a lesser extent, in patients with borderline abnormalities including subclinical hypothyroidism and isolated hypothyroxinaemia.[2] Crucially, the deleterious effects of overt disease are preventable by prompt correction of thyroid dysfunction.[5–7] Thyroid hormones are essential for normal foetal growth and brain development, and in early gestation, the foetus wholly relies on maternal thyroxine delivery up until the onset of foetal thyroid hormone secretion at 14–18 weeks.[8] This early phase of foetal life coincides with important developmental events including neuronal migration, proliferation and neural tube formation, and thus represents a period of critical vulnerability during which maternal thyroid dysfunction could have lasting repercussions.[8] Effective preconception management is a key strategy for optimizing thyroid disease outcomes in pregnancy, but focused reviews on preconception care are scarce. In this review, we highlight the evidence and rationale underpinning current preconception strategies and outline pragmatic approaches to preconception management of women with thyroid dysfunction.