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Thyroid hormone replacement in the preconception period and pregnancy.

Hypothyroidism is common in women of reproductive age and occurs in 2–3% of all pregnancies.1,2 Suboptimal thyroid function in pregnancy carries significant risks of poor obstetric outcomes including pregnancy loss and offspring neurodevelopmental impairment.2 These outcomes could potentially be improved through preconception care targeted at women of reproductive age with hypothyroidism. Most women with hypothyroidism are managed in general practice, and facilities for annual thyroid monitoring, medication reviews, and the maintenance of hypothyroidism disease registers, are available within existing primary care resources. In addition, the vast majority of women with hypothyroidism who become pregnant have pre-existing thyroid disease and are already established on treatment by the time of conception. Thus, opportunities abound in general practice to optimise thyroid hormone replacement and prepare women with thyroid dysfunction for conception. In this editorial, the authors discuss the challenges of preconception management of hypothyroidism and highlight current recommendations and a new patient education resource.

Thyroid hormones are essential for normal fetal growth and development.2 The devastating neurological consequences of severe iodine deficiency or neglected congenital hypothyroidism in children are now thankfully rare but remain grim reminders of the importance of thyroid hormones for fetal development. More subtle effects of thyroid hormone deficiency are widespread. Landmark studies in the 1990s showed that children born to women with uncorrected hypothyroidism during pregnancy had a 7-point IQ deficit compared to children of euthyroid mothers.3 Since then, numerous observational studies have shown increased risks of pregnancy loss and child neuro-intellectual impairment in untreated, as well as suboptimally treated, women with hypothyroidism.2,4 An adequate supply of thyroid hormones is particularly important in early gestation as the fetus cannot synthesise thyroid hormones until the second trimester, and before this time, relies …