An update on the safety of antithyroid drugs in pregnancy: the power of real-world data

Antithyroid drugs (ATDs) constitute the treatment option for the management of pregnant women with hyperthyroidism of Graves' disease. The risk of teratogenic side effects to the use of ATDs in pregnancy has challenged the clinical recommendation on the choice of drug and treatment strategy. Overview and methodological discussion of the evidence gathered within the last 50 years on the teratogenic risk of ATDs based on sources of real-world data (RWD) and different study designs. The level of evidence has evolved within the last century and current state of the art points toward a teratogenic role of Methimazole and Carbimazole. On the other hand, evidence to substantiate the teratogenic role of PTU is less comprehensive and less clear. The findings challenge clinical guidance, and uncertainties prevail for recommendations on the choice of ATD and individual patient management in and around early pregnancy. Future research should focus on the combined use of different sources of RWD in large cohorts and across populations. Detailed assessment of exposure and outcome and considerations on other thyroidal and non-thyroidal related factors in the associations observed are important to inform and support the clinical guidance.