Update on the safety of antithyroid drugs during pregnancy and lactation

Hyperthyroidism in pregnant and breastfeeding women should be adequately treated to prevent maternal and fetal complications. The choice of treatment during pregnancy and lactation is antithyroid drugs (ATDs). The risk of embryopathies in fetus and the effect on thyroid function of infants associated with the use of ATDs have been concerned for a long time. Large observational studies have quantified an increased risk of embryopathies associated with the use of methimazole (MMI) and propylthiouracil (PTU) during pregnancy, despite the effects of PTU appear less severe. Guidelines recommended PTU as the first-line choice for the first trimester during pregnant. And it is safe for ATDs use in lactating mothers. However, China Food and Drug Administration added the requirement of forbidden use of MMI during lactation this February. Accompanied by the updated guidelines for thyroid disease during pregnancy and the postpartum by American Thyroid Association, the issues of ATDs use during pregnancy as well as postpartum need to be further clarified. (Chin J Endocrinol Metab, 2018, 34: 634-637) Key words: Antithyroid drugs; Hyperthyroidism; Pregnancy; Lactation; Teratogenicity